Embedded Developer

A few weeks ago I promised an update on my experience using the PCBWay and Round Tracks plugins for KiCAD.

Well the boards are back and I must say they are looking good.

Rounded Tracks Plugin

The rounded tracks plugin certainly gives the 1970s feel to the PCBs. The batch ordered had a gloss black finish and this made the rounded effect a little difficult to see, a matt finish may have looked better or maybe even a green PCB for that real 1970s vibe.

This plugin has seen a little more use since the first order and here are a few things I have picked up:

• Apply teardrops after using the plugin
• Keep the original PCB layout

Adding teardrops to the board really does give the retro feel to the board. I have found that rounding the tracks after adding teardrops can leave a disjoint connection between the track at the teardrop connection to the pad.

So here is a section of the board with the rounded tracks applied after the teardrops:

Rounded Track Applied After Teardrop

This shows that the track exits the corner of the teardrop which is not ideal. Next we have the same pad with the rounded tracks applied before the teardrops:

Rounded Track Applied Before Teardrop

The second case is certainly more aesthetically pleasing.

The plugin asks if you want to apply the changes to the current PCB or if it should create a copy. I went for the halfway house and applied the changes to the PCB, reviewed and ordered the boards and then reverted the changes. This worked well as the plugin ran in under a second and allowed the retention of the original design. It is always going to be easier to apply any changes to the PCB on a board with angular tracks than it is to apply the changes to a board with rounded tracks.

PCBWay Plugin

This plugin really made ordering the PCBs a dream. The only thing to remember is to login to your PCBWay account before attempting to use the plugin. If you do this the plugin will create and upload a ZIP file with the gerbers directly to your PCBWay account. This allows the plugin to set all of the parameters for board dimensions and layers all seamlessly.

Finished Boards

Here is a photo of the finished board connected to a Meadow F7 Micro board running a sok test:

Meadow and OLED Display

Conclusion

The Rounded Tracks plugin is only really of interest if you want the retro 1970 look and feel to the final PCB. The PCBWay plugin is really useful as it streamlines the ordering process and removes the need to manually create the gerber files and upload them to the PCBWay website.

A recent change to a PCB design has given the opportunity to try out a couple of KiCad plugins. The board is a simple one and is used to provide feedback when running network soak tests. The board is designed for the Meadow ecosystem and is a fairly simple design consisting of:

• SSD1306 OLED display
• Indicator LEDs
• Reset button
• Headers to connect the board to a Meadow board

The board has been tested and it works well. The changes doubled the number of LEDs and changed some of the components footprints.

Round Tracks

The concept behind Round Tracks is simple, take a PCB layout and give the tracks the feel of the 1970s. It does this by taking the layout and looking for any tracks that change direction. The plugin then takes these tracks and rounds the corners.

Applying this to the OLED PCBs gives the following output:

PCBWay Plug-in for KiCad

The next plugin is the PCBWay plugin. This should take the PCB layout and generate a zip file to upload to the PCBWay web site for manufacture. It appears to be really simple to use and starts an order for you and then uploads the files into the order.

Order submitted and now we just have to wait for the PCBs to arrive.

Conclusion

Manufacturing is complete and they are now on their way. There is going to be a small wait while the PCBs make their way from China to the UK and then we can see how the plugins faired.

Update to follow in a few weeks.

For the last year or so, the goto scope in the lab has been a Rigol MSO5104. This is a 100MHz, 4 channel scope with 16 digital channels. Connectivity options include USB and wired LAN. The LAN connection allows the scope to be controller via a web control panel which is great for interactive control from a host computer but is not much use for automation.

Enter pyvisa.

Hackaday Article

Hackaday published an article Grabbing Data From a Rigol Scope with Python in late November of 2023. It appears that I am not the only one looking to control a Rigol oscilloscope from a host computer.

The article discusses using pyvisa to communicate with a DHO900-series scope not a MSO5000-series scope, let’s see if the same commands will work with the MSO5104.

Communicating With The MSO5104

First up, try to connect to the scope over the LAN:

import pyvisa
visa = pyvisa.ResourceManager('@py')
scope = visa.open_resource('TCPIP::192.168.1.95::INSTR')

So that seemed to work, so let’s try to get the scope to identify itself:

scope.query('*IDN?')
'RIGOL TECHNOLOGIES,MSO5104,MS5A*********,00.01.03.03.00\n'

So far, so good, the * characters represent part of the devices serial number. Now let’s try a few commands to see if we can make the scope to do something:

scope.write(':SINGLE')
9

This changes the mode of the scope to single shot and the Single button turned on as if it had been pressed. The return value is the number of characters sent to the scope.

Conclusion

It appears that the original Hackaday article is going to be part of a series of articles as a follow-up article was published a few days later (see Scope GUI Made Easier). This could turn into something useful.

Upgrading machines is always an interesting experience, reinstalling software and drivers. The latest update from an Intel Mac to Apple silicon was no exception. The majority of the process went to plan with the only major issue being the installation of the Dell 1320c printer driver.

Some History

The Dell 1320c printer is a fairly old colour laser printer and this device is about 12 years old but it has seen very light service. Replacing a such a lightly used machine is not only environmentally unfriendly but also an unnecessary expense.

Driver support for this printer has always been patchy on newer machines which is understandable. The trick with this printer is not to install it as a Dell 1320c printer but instead use the Xerox C525 driver.

This year has seen several failed attempts to install the driver on Apple silicon machine with the latest attempt working, hence this post in case it helps others (and also my future self).

Installing the Driver

The driver can be installed by following these steps:

1 – Open the Printer and Scanner Settings

Open the Printer and Scanner settings and click the Add Printer, Scanner or Fax.. button.

Add New Printer

2 – Add Printer Properties

The printer being installed in a network printer and completing the IP address allows the computer to find the printer and complete some of the printer properties.

Add Printer Dialog

Two setting need to be changed. The first is the Protocol, this should be set to HP Jetdirect – socket.

The second setting that needs to be changed is the driver. Click the Use drop down and select Select Software…. This will present you with the Printer Software dialog.

3 – Install the Xerox Driver

In the Printer Software dialog, search for C525 and select the Xerox C525 A v3.2 driver.

Printer Software Dialog

Click the OK button to add the printer.

The only thing is to test the installation by printing a test page.

Conclusion

Getting the Dell 1320c driver installed is not difficult, it is simply a case of knowing the tricks to get it working. This is something that is only performed every few years and hopefully this will help the next time this driver need to be installed on a new machine.

This blog serves two purposes:

• Sharing information that I hope is useful to others
• Aide-Memoire for yours truly

This post falls into the second group, something I’ve done in the past but forgotten.

Background

The current project requires the test environments to be expanded. Several of the environments are running on Raspberry Pi SBC which is feasible now that they are available in volume once again. There is one exception, a Mac Mini with a M1 processor. This environment allows the usual tests to be run in the same manner as the Raspberry Pi boards. It also gives the ability to build the code and attach a debugger to the board invaluable for tests that are known to be failing and need to run for an extended period of time.

This sort of setup is ideal for running headless, no monitor, keyboard or mouse; we can just use MacOS screen sharing and ssh.

What is Wrong?

Enter a new (well secondhand) Mac Mini. Setup went well, attached a keyboard and mouse and ran through the setup process with no issues. Logged on to the Mac and all is well. A few configuration tweaks to enable screen sharing and remote login were required, nothing too complex, just a case of setting the right permissions.

Next step, test the remote connection. Screen sharing started OK and the Mac appeared on the network with file sharing enabled. Time for a reboot.

System rebooted OK, time to browse the network.

The new machine was not showing in the network browser and ssh was able to establish the connection.

Back to the still connected keyboard and mouse to log on. Once logged in the system once again appeared in the network browser and screen sharing and ssh worked flawlessly.

Time for another reboot and the same thing happened, machine booted OK but nothing appeared on the network until a successful login through the attached keyboard and mouse.

The Solution

This is where it gets odd. Apparently, you have to turn FileVault off. That’s right you have to turn the disc encryption off in order to enable fully remote logon.

FileVault is turned on automatically during the MacOS installation processes which makes sense. Disc encryption will make it harder for a malicious actor to recover sensitive information from a machine, so disc encryption on modern machines is good. The side effect of this is that you must logon to the Mac via an attached keyboard before it will turn up on the network.

Conclusion

I have a solution of sorts but I do find it odd that disc encryption must be disabled before remote services can be enabled on the Mac. After all, if you require remote access to a system then you are likely to be putting the physical machine in a location where access is going to be difficult.

There are somethings in software development that we do not do very often and because we perform the task infrequently we often forget the nuances (well I do). One of these tasks is creating a new project.

In this post we will look at one option for automating this process, GitHub Templates. This work is partially my own work but also a case of bringing together elements of other blog posts and GitHub repositories.

All of the code discussed below can be found in the PicoTemplate repository and this should be used as a reference throughout this post.

Starting a New Project

Several days ago, I was in the process of starting a new project for the Raspberry Pi Pico W using the picotool. For those who are not familiar with this tool is is meant to automate the project creation process for you. You simply tell the tool which features you are going to be using and a few other parameters like board type and it will generate a directory containing all of the necessary code and project files.

Sounds too good to be true. For me it was as no matter which feature list I requested I could not get an application to deploy to the board and talk to the desktop computer over UART or USB.

At this point I decided to take this back to basics and get Blinky up and running. The problem definition became:

1. C++ application
2. Blink the onboard LED
3. Support both Pico and Pico W boards
4. Standard IO output over UART or USB

It would also be desirable to automate as much of the process as possible.

Blinky

One complication with the Pico boards is that they both use a different mechanism to access the on board LED. The Pico has the LED wired directly to GPIO 25 whilst the Pico W uses a GPIO from the onboard WiFi / Bluetooth chip (hereafter referred to as just wireless). This means we have different versions of Blinky depending upon which board is selected. This also means that the Pico W board also needs an additional library to support the wireless chip even if we are not using any wireless features.

The simplest way of doing this is to use a template directory to contains the main application code and the project CMakeFileList.txt file for each board. We can then copy the template files for the appropriate board type into the sources directory.

Keeping with the theme of forgetting the nuances, we will add some scripts to perform some common tasks:

1. Configure the system (copying the files to the correct locations)
2. Build the application
3. Flash a board using openocd

Our first task will be to set the system up with the correct main.cpp and CMakeFileList.txt files and put the files in the correct place. Checking the default CMakeFileList.txt file we see that the project is named projectname which is not very informative so the configuration script will also rename the project as well.

The purpose of the build script should be obvious, it will build the application code and also offer the ability to perform a full rebuild if necessary.

The final script will flash the board using openocd using another Raspberry Pi Pico configured as a debug probe. This was discussed a few weeks ago in the post PicoDebugger – Bringing Picoprobe and the PicoW Together. This set up also has the advantage of exposing the default UART to the host computer.

Using the Scripts

Using the scripts is a three step process, one of which is only really performed once.

The first step is to use the configure.sh script to copy the files and rename the project:

./configure.sh -b=picow -n=TestApplication

After running this command the src/main.cpp file will contain the code to blink the LED on a Pico W board and the project will have been renamed TestApplication.

Secondly, we can build the application using the build.sh script:

./build.sh

Finally, the application can be deployed to the board using the flash.sh script.

./flash.sh

The UF2 file (in the case above, TestApplication.uf2) can also be copied to the board if a debug probe is not available.

Scope Creep

The story was supposed to end here but this is not going to be the case.

There are some improvements that we can look at to make the system a little more comprehensive. These include:

1. Add a testing framework
2. Create a Docker file for build and testing

Both of these items are currently work in progress.

Acknowledgements

This project has been inspired by several others on github:

• [Raspberry Pi Pico Examples](https://github.com/raspberrypi/pico-examples)
• [Raspberry Pi Pico Template](https://github.com/cathiele/raspberrypi-pico-cpp-template)

Conclusion

The initial requirement of creating a template for Pico and Pico W development could have been achieved simply by creating two different templates, one for each board type. This would arguably have been quicker and less complex.

The addition of the testing framework and docker container into the requirement would have resulted in some duplication of work in each template. This made bringing the two templates together in one repository more logical as errors or additions in one project type are automatically part of the other board template.

Recent work has involved reviewing some test environments for an IoT development board. The aim is to improve some of the components used for testing as well as adding new functionality. The requirements are:

• Provide an updated version of existing functionality
• Single board environment with all functionality deployed for quick testing
• Cluster distributing the test environment for load testing

The most cost effective way to do this is to use a number of Raspberry Pi single board computers. These boards are now becoming available in quantities after several years of limited availability.

The Problem

How to setup the environment in such a way that will allow a fresh environment to be created reliably.

Enter ansible.

Ping

First step, try to contact a board and this is where ping comes in. This command will verify that ansible can connect to a board. The following command will test the connection to each board:

ansible cluster -m ping -i hosts

This command requires a text file hosts containing the list of boards to the contacted. The file is simple and may only contact two lines:

[cluster]
node

In the above example, the file defines a group of machines to be contacted and this is named cluster and in this case the group contains only one machine and this is named node. The name cluster is also mentioned in the ansible command above.

Additional machines can also be named under the cluster entry by simply placing additional entries on a new line in the file.

So far this is nothing new and it is covered in the Ansible documentation.

What Happened

The first step was to use the Raspberry Pi Imager application to create a new image on a new SSD. Nothing complex:

• Raspberry Pi 64-bit Lite OS
• Set the machine name to be node
• Enable SSH
• Set the user name to clusteruser and give the user a secure password

The password was then stored on the local machine in an environment variable CLUSTER_PASSWORD to allow the scripts to be stored in source control without giving away any secrets.

Time to test the connection with the following command:

ansible cluster -m ping -i hosts --extra-vars "ansible_user=clusteruser ansible_password=$CLUSTER_PASSWORD"

Breaking this down, we want to ping all of the machines defined in the cluster group. The group is defined in the file hosts and we are going to log on to the machines with the user name clusteruser and with the password contained in the CLUSTER_PASSWORD environment variable.

Now running the above command results in the following:

node | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}

Conclusion

A good start to the project, now on to something more complex, time to install and configure some software.

And I can’t believe I’ve missed Ansible for so long.

It may appear at the start of his story that this is an unhappy tale, but bear with it, there is a happy ending.

Having an oscilloscope when working with electronics is a must even for hobbyists. The amount of information you can gather about the behaviour of a circuit is invaluable. The daily workhorse here is the Rigol MSO5104 Mixed Signal Oscilloscope.

This scope is really a small computer and like all computers a regular check for firmware updates is always a good idea. A recent visit to the Rigol web site resulted in a new firmware version downloaded to the laptop.

Time to Install

Installation should be a quick process:

• Extract the files on the PC
• Copy the firmware file (.gel file) to a USB drive
• Connect the USB drive to the oscilloscope and select Local Update from the System menu

Following the process resulted in the update dialog being shown with a progress bar followed by instructions to restart the oscilloscope.

Power cycling the oscilloscope presented the expected Rigol logo along with a progress bar, so far, so good. The boot continued until just before the end of the process bar and then it stopped.

Wait a little while longer.

No movement after 5 minutes, time to power cycle. The same thing happened. Rinse and repeat, still no progress.

Time to call the local distributor.

Recovery

A call to the local Rigol distributor in the UK was in order. I found their technical support really good. In fact it was FAN-TAS-TIC. The solution turned out to be fairly simple.

• Power off the oscilloscope
• Turn the oscilloscope on again
• As the oscilloscope starts press the Single button repeatedly

Doing this would eventually show the Rigol logon on the screen with two options:

• Upgrade Firmware
• Recover Defaults

Selecting Recover Defaults took us through the recovery process and after a few minutes restoring the configuration and restarting the oscilloscope it was back up and running again.

Conclusion

Computers are all around us running in everything including the modern oscilloscope. Rigol has thoughtfully added a recovery mechanism into the firmware update process and so today all was not lost.

A call out to the UK distributors, the support was really, really good.

Time for some more experimentation with NuttX, today serial LCDs.

Serial LCDs

Small LCD displays can be found in many scientific instruments as they provide a simple way to display a small amount of information to the user. Typically these displays are 16×2 (2 lines of 16 characters) or 20×4 (4 lines of 20 characters) displays. The header to this article shows part of the output from a 20×4 display.

Communication with these displays is normally through a 4 or 8 bit interface when talking directly to the controller chip for the LCD. Using 4 or 8 data lines for communication with the LCD is a large burden on a small microcontroller. To overcome this, several vendors have produced a backpack that can be attached to the display. The backpack uses a smaller number of microcontroller lines for communication while still being able to talk to the LCD controller chip.

This post looks at using such and LCD and backpack with NuttX running on the Raspberry Pi Pico W.

NuttX Channel (Youtube)

A great place to start with NuttX is to have a look at the NuttX Channel on Youtube as there are a number of quick getting started tutorials covering a number of subject. In fact there is one covering a 16×2 LCD display which is similar to what will be used in this tutorial, with a small difference.

The video linked above covers a lot of what is needed to get 16×2 LCD up and running. There are some small changes that are needed as NuttX has moved on since the video was released.

Hardware

The major changes compared to the video above are:

• Microcontroller used will be the Raspberry Pi Pico W
• LCD display will be 20×4 display

The LCD display used here will be a larger physical display (20×4 instead of 16×2) but it will still use the same interface on the backpack, namely the PCF8574 GPIO expander. This uses I2C as a communication protocol so reduces the number of GPIO lines required from 8 to 2.

There are two I2C busses on the Pico W, I2C0 and I2C1 and in this case I2C1 will be the chosen interface. Something that caused some issues but more on that later.

For now we start with a base configuration with the LCd connected to GPIO6 and GPIO7 on the Pico W.

Configuring NuttX

Configuration followed much of the video linked above enabling the following:

• Enable I2C master and I2c1 in the System Type menu
• I2C Driver Support in the Device Drivers menu
• PCF8574 support through Device Drivers, Alphanumeric Drivers menus
• Segment LCD CODEC in the Library Routines menu
• Segment LCD Test in the Application Configuration, Examples menu

Time to build, deploy and run.

• make clean followed by make -j built the system
• The application was then deployed to the Pico W and board was reset
• The application can be run by connecting a terminal/serial application to the board an running the command slcd

Nothing appears on the display. Time to check the connections and break out the debugger.

Troubleshooting

Checking the connections showed that everything looked to be in order. The display was showing a faint pixel pattern which is typical of these displayed when they have been powered correctly but there is no communication. Double checking the I2C connections showed everything in theory was good.

Over to the software. Running through the configuration again and all looks good here. So lets try I2C0 instead of I2C1, quick change of the configuration in the software and moving some cables around and it works!

So lets go back to the I2C1 configuration, recompile and deploy to the board and it works. What!

It turns out that I had not moved the connections from I2C0 back to I2C1.

The default application was also only displaying 1 line of text. So let’s expand this to display 4 lines of text, namely:

• Hello
• Line1
• Line2
• Line3

Running the application gives only two line of text:

• Hello
• Line3

How odd.

Lets Read the Sources

After a few hours of tracing through the sources we find ourselves looking in the file rp2040_common_bringup.c where there is this block of code:

#ifdef CONFIG_LCD_BACKPACK
    /* slcd:0, i2c:0, rows=2, cols=16 */

    ret = board_lcd_backpack_init(0, 0, 2, 16);
    if (ret < 0)
    {
        syslog(LOG_ERR, "Failed to initialize PCF8574 LCD, error %d\n", ret);
        return ret;
        return ret;
    }
#endif

This suggests that the serial LCD test example is always configured to use a 16×2 LCD display on I2C0. This explains why we saw only two lines of output on the display and also why the code did not work on I2C1.

Changing ret = board_lcd_backpack_init(0, 0, 2, 16); to ret = board_lcd_backpack_init(0, 1, 4, 20); and recompiling generated the output we see at the top of this post.

Navigating to the System Type menu also allowed the I2C1 pins to be changed to 26 and 27 and the system continued to generate the expected results.

Conclusion

This piece of work took a little more time than expected and it would have been nice to have had the options within the configuration system to change the display and I2C parameters. As it stands at the moment using a 20×4 display requires changes to the OS source code. This is a trivial change but it does make merging / rebasing with later versions of the system a little more problematic.

A while ago I put together an emulator for the Small Scale Experimental Machine (SSEM), also known as the Manchester Baby. This was a basic console application allowing a program written for the Manchester Baby to be run in a console application on a modern computer. As things turned out, I now spend most of my time working in either C or C++. This has left me with a piece of code that is difficult to maintain as I have to relearn Python every time I want to make any improvements.

Time to rewrite the application in C++.

SSEM Simulator

The simulator provides a number of features:

• Assembler/compiler to take source files and generate the binary to be execution
• Console interface to control the execution of the application
• Simulated display of the registers and memory

More information about the Python version of the simulator can be found in this blog and on the Small Scale Experimental Machine web site with full source code available on GitHub.

Porting the Simulator

The aim of the initial port is to provide the same functionality of the original application with any changes necessary to provide additional robustness as we are undoubtedly going to be seeing pointers in the C++ port.

Where possible, the structure of the original Python code has been maintained to keep a 1:1 mapping with the original code and test suite. This will provide an easy way to validate the unit tests in the port against the original Python code. The original Python code was validated against David Sharps Java Simulator.

The long term aim of this port is to provide a way of running the application on a Raspberry Pi Pico connected to hardware which will emulate the original SSEM. The application on the Raspberry Pi Pico will target the NuttX RTOS. As we will see later, compiling and running on NuttX will present some interesting issues.

Initial Port

The first stage of the port is to reproduce the core functionality of the SSEM showing the application output in a console interface targeting C++ 17. The only real complication here is ensure the user interface and platform specific code are abstracted to keep as much functionality in common with a desktop and NuttX implementation as possible.

The original Python code and the C++ port can be found in the Manchester Baby GitHub repository. A quick check of the source code shows that the 1:1 mapping has been kept where possible. The only real significant difference between the two code bases is the separation of the unit tests from the class implementation. The Python code keeps the unit test code in the class definitions themselves, the C++ code implements the unit tests in their own files.

Memory Checks

The switch from Python to C++ brings a new danger, memory access issues and memory leaks.

One memory issue that we can address relatively easily is memory leaks. If we can abstract the core functionality into a self contained group of files then we can use valgrind to check for memory leaks. A small glitch with using valgrind is that the application is not available for Mac from the key repositories. There is an informal project on GitHub.

The issue of valgrind not running on the mach was resolved by putting together a Dockerfile containing common development tools. The memory check could then be run on the desktop using Docker.

Running the Emulator

The emulator can be run on both a desktop computer as well as a board running NuttX.

Run from the Desktop

Running the application on the desktop is the simplest way to test the emulator:

• Open a command console and change to the Desktop directory in the repository
• Build the emulator with the command make
• Run the emulator with the command ./ssem_main

Run on NuttX

Running on NuttX is a little more complex as we need to build the application and the operating system and then deploy the binary to a board. The processes of adding the SSEM application to a Raspberry Pi PicoW board has already been documented in the article Adding a User Application to NuttX. The first step is to follow the steps in the article to add the SSEM basic applicatiom.

The next stage is to copy the contents of the NuttX directory over the application directory created in the above article. The code should then be rebuilt with the command make clean && make -j. The application can now be deployed to the board.

Now we have the OS and the application deployed to the Raspberry Pi (or your board of choice) we can connect a serial adapter to the board and press the enter key twice. This will bring up the NuttX shell. Typing help should show the ssem application deployed to the board. Simply execute this by entering the command ssem.

Application Output

In both cases the emulator should run the hfr989.ssem application (the source for this can be found in the SSEMApps folder in the repository). Both the desktop and the NuttX versions of the emulator will run the SSEM application and will show the start and end state of the SSEM on the console / serial port. The first output will show the SSEM application loaded into the store lines:

NuttShell (NSH) NuttX-10.4.0
nsh> ssem
                   00000000001111111111222222222233
                   01234567890123456789012345678901
   0: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
   1: 0x48020000 - 01001000000000100000000000000000 LDN 18           ; 16402
   2: 0xc8020000 - 11001000000000100000000000000000 LDN 19           ; 16403
   3: 0x28010000 - 00101000000000010000000000000000 SUB 20           ; 32788
   4: 0x00030000 - 00000000000000110000000000000000 CMP              ; 49152
   5: 0xa8040000 - 10101000000001000000000000000000 JPR 21           ; 8213
   6: 0x68010000 - 01101000000000010000000000000000 SUB 22           ; 32790
   7: 0x18060000 - 00011000000001100000000000000000 STO 24           ; 24600
   8: 0x68020000 - 01101000000000100000000000000000 LDN 22           ; 16406
   9: 0xe8010000 - 11101000000000010000000000000000 SUB 23           ; 32791
  10: 0x28060000 - 00101000000001100000000000000000 STO 20           ; 24596
  11: 0x28020000 - 00101000000000100000000000000000 LDN 20           ; 16404
  12: 0x68060000 - 01101000000001100000000000000000 STO 22           ; 24598
  13: 0x18020000 - 00011000000000100000000000000000 LDN 24           ; 16408
  14: 0x00030000 - 00000000000000110000000000000000 CMP              ; 49152
  15: 0x98000000 - 10011000000000000000000000000000 JMP 25           ; 25
  16: 0x48000000 - 01001000000000000000000000000000 JMP 18           ; 18
  17: 0x00070000 - 00000000000001110000000000000000 HALT             ; 57344
  18: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  19: 0xc43fffff - 11000100001111111111111111111111 HALT             ; -989
  20: 0x3bc00000 - 00111011110000000000000000000000 JMP 28           ; 988
  21: 0xbfffffff - 10111111111111111111111111111111 HALT             ; -3
  22: 0x243fffff - 00100100001111111111111111111111 HALT             ; -988
  23: 0x80000000 - 10000000000000000000000000000000 JMP 1            ; 1
  24: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  25: 0x08000000 - 00001000000000000000000000000000 JMP 16           ; 16
  26: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  27: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  28: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  29: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  30: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  31: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0

Reading from left to right, the above output shows the following:

• Store line number (i.e. the memory address) 0:, 1: etc.
• The hexadecimal representation of the store line contents.
• Binary representation of the store line contents
• Disassembled representation of the store line contents JMP 0 etc.
• Decimal representation of the store line contents

It must be remembered when reading the above that the least significant bit is at the left of the word and the most significant bit is to the right. This is honoured with the hexadecimal and binary components of the above output. The decimal value to the right should be read in the usual way for a base 10 number.

After a short time the contents of the store lines at the end of the run will be displayed:

Program execution complete.
                   00000000001111111111222222222233
                   01234567890123456789012345678901
   0: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
   1: 0x48020000 - 01001000000000100000000000000000 LDN 18           ; 16402
   2: 0xc8020000 - 11001000000000100000000000000000 LDN 19           ; 16403
   3: 0x28010000 - 00101000000000010000000000000000 SUB 20           ; 32788
   4: 0x00030000 - 00000000000000110000000000000000 CMP              ; 49152
   5: 0xa8040000 - 10101000000001000000000000000000 JPR 21           ; 8213
   6: 0x68010000 - 01101000000000010000000000000000 SUB 22           ; 32790
   7: 0x18060000 - 00011000000001100000000000000000 STO 24           ; 24600
   8: 0x68020000 - 01101000000000100000000000000000 LDN 22           ; 16406
   9: 0xe8010000 - 11101000000000010000000000000000 SUB 23           ; 32791
  10: 0x28060000 - 00101000000001100000000000000000 STO 20           ; 24596
  11: 0x28020000 - 00101000000000100000000000000000 LDN 20           ; 16404
  12: 0x68060000 - 01101000000001100000000000000000 STO 22           ; 24598
  13: 0x18020000 - 00011000000000100000000000000000 LDN 24           ; 16408
  14: 0x00030000 - 00000000000000110000000000000000 CMP              ; 49152
  15: 0x98000000 - 10011000000000000000000000000000 JMP 25           ; 25
  16: 0x48000000 - 01001000000000000000000000000000 JMP 18           ; 18
  17: 0x00070000 - 00000000000001110000000000000000 HALT             ; 57344
  18: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  19: 0xc43fffff - 11000100001111111111111111111111 HALT             ; -989
  20: 0x54000000 - 01010100000000000000000000000000 JMP 10           ; 42
  21: 0xbfffffff - 10111111111111111111111111111111 HALT             ; -3
  22: 0x6bffffff - 01101011111111111111111111111111 HALT             ; -42
  23: 0x80000000 - 10000000000000000000000000000000 JMP 1            ; 1
  24: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  25: 0x08000000 - 00001000000000000000000000000000 JMP 16           ; 16
  26: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  27: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  28: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  29: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  30: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
  31: 0x00000000 - 00000000000000000000000000000000 JMP 0            ; 0
Executed 21387 instructions in 30000000 nanoseconds

The original SSEM ran at about 700 instructions per second, modern PCs and even RP2040 processors are running the application much faster.

Conclusion

Even small boards (such as the Raspberry Pi Pico) running relatively low power processors can now emulate the Manchester Baby running application intended for the SSEM many times faster that the original hardware. The hfr989.ssem application would have run in about 30 seconds in 1948, today we can run this in an emulator in less that 30ms.