Random (old) tech

Amiga Spice

Sat, 20 Sep 2025 15:00:03 +0100

SPICE is a program for simulating electronic circuits, the name is an acronym that stands for "Simulation Program with Integrated Circuit Emphasis". Originally the program was created by Laurence Nagel at the Electronics Research Laboratory of the University of California. It was released as public-domain and the release included the source code, which then meant that it was possible to port the program to other systems, including the Amiga.

More information about the history and other versions of SPICE can be found on its Wikipedia page and on the SPICE download page of Berkeley University.

SPICE is a valuable tool when designing electronics. It provides an important step between creating the design and building the first prototype. Back in the early nineties when I was studying electronic design the use of SPICE was part of the curriculum. At home I used the Amiga version, which happened to be slightly newer than the version we used in class. And I still tend to use a descendant of the original program as part of my job, but now in the guises of LTspice and Ngspice that run on a modern PC.

The Amiga version I'm now going to use is version 3f5, which can be found on Aminet compiled for 68000 or for 68020 with FPU. This article is not intended as a tutorial, but more as an example of using the Amiga for productivity. I'll try not to get too technical.

Using SPICE 3f5

SPICE is a command line tool and takes a text file with a description of the electronic schematic as its input. The text file will also contain commands that describe the type of calculations SPICE needs to perform. After performing these calculations SPICE will print the result back to the CLI/Shell window by default.

The input file

The very first line of the input file is treated as the name of the circuit. Lines that start with an asterisk are treated as comments and skipped when the file is processed. Circuits are described by placing a component on each line with its connections and value(s).

The image below shows on the left a simple low-pass filter consisting of resistor R1 and capacitor C1. The input signal is produced by AC voltage source V1. Each node (connection point) in the circuit is given a number and these numbers are used in the input file to describe where each component in the circuit is situated. Below on the right the SPICE description for the circuit on the left is shown.

Low-Pass Filter

* Circuit description
R1 1 2 10
C1 2 0 10u
V1 1 0 DC 0 AC 1

* Commands
.AC DEC 10 10 100k
.plot AC V(2)

.end

The description shows that R1 sits between node 1 and 2 and has a value of 10 Ohm. C1 sits between 2 and 0 and has a value of 10 micro Farad. The voltage source is connected to node 1 and 0, has no DC voltage, but has an AC voltage of 1 Volt.

The input file also contains the commands that tell SPICE what to calculate. Commands for SPICE always start with a period. In the example above the AC command is used to step the frequency of the AC signal from 10Hz to 100kHz and to do this in 10 steps for each decade - in this case there are four decades (10Hz to 100Hz, 100Hz to 1kHz, 1kHz to 10kHz and 10kHz to 100kHz) so there will be 40 calculation points.

Then the plot command tells SPICE that the resulting AC voltage on node 2 (the output node of the filter) is of interest and should be plotted to a graph.

The end command is there to indicate the end of the file.

The output

Older versions of SPICE would just take the input file as an argument and spit the output to the terminal. Newer versions (like the version 3f5 from Aminet) also have an interactive mode. To process the file like the older versions did, the "-b" argument is used:

> spice3f5 -b rc-filter.cir

A screenshot of the output is shown below at the left. For the original UNIX version of SPICE this output was meant for a line-printer so that the graph looked fine when the printout was turned from portrait to landscape orientation. The image below on the right shows the same screenshot, but rotated counter-clockwise to give a similar effect.

The graph on the rotated image shows the voltage on node 2 (the filter output) on the vertical axis and the increasing frequency from left to right on the horizontal axis. On the left hand side the AC voltage is passed on without any change, in the middle the filter removes more of the signal as the frequency goes up. At the right hand side nothing of the input signal is left on the output. As expected, the low-pass filter will only pass the low frequencies.

Interactive mode

SPICE 3f5 will go into interactive mode when it is started without the "-b" argument:

> spice3f5 rc-filter.cir

It will load the input file and then give a command prompt, which allows the user to give the program commands. To execute the calculation command in the input file run is typed on the SPICE command prompt. The prompt will return without any output if no issues were encountered running the command.

To see the output of the calculations the command plot v(2) is typed on the prompt. Again the prompt returns without printing anything, but this time a graphical screen will have opened behind(!) the Workbench screen showing the requested plot:

In interactive mode it is not required to have any commands in the input file. Instead of running the commands in the input file the user can just type the commands on the prompt to have SPICE do the calculations.

The interactive mode also allows the user to modify the values of the components in the circuit with the alter command. The following command sequence changes the value of R1 to 100 Ohm (it was 10 Ohm) then recalculates the frequence analysis and ends with plotting the new graph to see what effect changing the value of R1 had.

Spice 4 -> alter r1=100
Spice 5 -> ac dec 10 10 100k
Spice 6 -> plot v(2)
Press <return> to continue.
Spice 7 ->

SPICE will use the previously opened screen for the new plot, so it will ask to press <return> to continue before it erases the screen and draws a new plot on it. The plot with the new value of R1 is shown below. Increasing the value of R1 has moved the graph to the left, meaning that the filter starts working at a ten times lower frequency than before.

The interactive mode gives the user more flexibility to make changes and quickly see the result. It also allows the user to perform different types of calculations and see the output of those. Without the interactive mode each of these changes would require a modification to the input file, which makes it a bit more cumbersome - especially for complex circuits.

Here is an overview of a small number of SPICE commands. A full list of commands can be found on the Tclspice website, which is another SPICE3 implementation.

alter	Change a value or parameter.
display	Give a list of all variables that can be printed/plotted.
help	Show a very long help text.
run	Run the calculation commands from the input file.
show	Show details of a particular component. For example "show R1" to see information about R1 (value, voltage, current, etc). To see information about all components use "show all".
quit	Leave the interactive mode and exit the program.

Other Amiga versions

The 3f5 version used here is not the only version of SPICE that is currently available on Aminet. There is an older version called ASpice on Aminet as well. This is a port of SPICE2 and this is the version I used when I was studying.

Another SPICE version that is available on Aminet is called AmiSPICEed. This version boasts a graphical editor for creating the circuits and that got me quite excited - this sounded like an Amiga version of something like LTSpice. But unfortunately I've not been able to get it to run properly on any of my systems. I tried different Kickstart versions, Workbench versions and even screen resolutions. The button images are always completely scrambled. That is a pity since it would have showcased one of the Amiga's strong points: the GUI.

Conclusion

The rules of nature have not changed and as such the results calculated by these older versions of SPICE are still correct. Since a lot of the newer versions of SPICE were built on top of SPICE3 a lot of information that is still available on the web is compatible with the way the Amiga version 3f5 works. Due to the lack of a graphical editor describing a complex circuit in a text file can be difficult, although a lot of modern CAD programs do have the option to export a circuit as a SPICE compatible netlist.

For my day job I'll continue to use modern versions like LTspice and Ngspice. For my less complex hobby projects I think I'll revisit the Amiga version of SPICE 3f5 more often. I may even have a look at using the Amiga to calculate through the BassMX frequency response. Something I used LTspice for during development.

The Maycom Easycorder

Sun, 31 Aug 2025 15:00:55 +0100

In a previous post I wrote about the Maycom Digicorder, which was a very early (likely the first) portable solid state digital recorder. This post caused an owner of a Maycom Easycorder to contact me and send me their (non working) Easycorder. The Easycorder is the product that Maycom created as a follow-up to the Digicorder. It is also one of the products I worked on from the outset together with 4 other technical colleagues. I mainly worked on the low level audio driver and the communication functionality.

Just like with the Digicorder there is not much information on the Internet (although this time there is a snapshot of the Maycom web site on the Wayback machine) so I dived back into my folder of Maycom memorabilia to produce this post.

The design goals

Feedback from Digicorder customers as well as Maycom employees was used to setup the design goals for the Easycorder. Assembly of the Digicorder during manufacturing was rather elaborate and this was one of the points the engineers wanted to address. Customers mentioned that they'd like less weight, longer battery life and lower cost. Another point that customers brought up was the price of the PCMCIA flash card media. At the time a 40MB card could cost anywhere between 500 to 800 US dollars. A MiniDisc with a larger recording time at that time would cost only a couple of dollars. Managers at radio stations were very worried about their staff losing the Digicorder's expensive storage cards.

The Easycorder was going to use MPEG Layer 2 audio compression (just like the Digicorder), which allowed a broadcast quality mono audio file to be compressed to about 1MB per minute. Files were going to use the Broadcast Wave Format, which was in the process of being adopted as the standard for importing audio into radio automation systems.

The solutions

The decision was made to use a more traditional design for the Easycorder. It therefore used plastic and metal for the case and was shaped more like a traditional recorder. This made the recorder much easier to assemble/manufacture and also much lighter since a lot of the Digicorder's weight was due to the heavy duty Nyrim case.

Two versions of the case were chosen, one in a black/grey colour scheme (named "the Classic") and one in a striking blue/silver scheme (named "the Sport"). Most of the people working at Maycom preferred the blue/silver of the sport version, but marketing was worried that the more conservative broadcasters would regard it too toy-like in that colour scheme. This was not an unreasonable view and thus the classic version was added tot he product line. The images below show two Maycom promotional images, one for the "Sport" on the left and one for the "Classic" on the right. Functionality of the two types is 100% identical.

To improve battery life the new recorder was made considerably more power efficient and used a specifically designed battery pack (instead of using an off the shelf one). This ensured that good quality cells with a high quality charging circuit were used, something not always guaranteed with cheap packs from home improvement stores. The new pack not only improved the operation time, it also increased the number of charging cycles each battery pack could handle before losing too much charge.

The Easycorder still features two PCMCIA card slots, but one of these is internal to the recorder and can't be accessed by the user. This was done to alleviate the worry about staff losing an expensive flash card. Since the card was now permanently fixed inside the recorder it could no longer be lost. The second slot is accessible via a slot in the side of the recorder and can be used for recording, but also for file transfer.

Compared to the Digicorder, the cost of the recorder was reduced by using a less expensive chipset, removing the ISDN terminal adapter and making overall manufacturing and assembly easier and less time consuming. The new chipset did not allow the same variable speed playback (so called "scrub editing" or "scrubbing", where a jog wheel is used to set the speed and direction of the audio playback) and editing features were not planned for the recorder, to limit development time and cost to the end user. On the Digicorder the editing functionality was mainly used to limit the size of files before transfer over ISDN and the Easycorder did not have this capability (more about this later).

The result (case design)

Here are some photographs of the Sport version of the Easycorder. The following image shows the front of the recorder. This is the same promotional image that was used earlier to show the difference between the Classic and the Sport version.

All buttons are on the front of the device and there is a mount on each side of the recorder for a shoulder strap. When the recorder is hanging from the user's shoulder all buttons will be facing the user. This makes operation out on the street easy. The power button and the push buttons on the right hand side have a glow ring around them to make them more visible in low-light situations as shown in the image below. Yes, I was quite chuffed when I got the recorded working again!

On the left hand side of the case the digital audio inputs and outputs can be found. Here is also where a an extended capability parallel port is situated that is used for file transfer between the recorder and a Windows PC (or laptop). The largest space on this side of the recorder is taken up by the type-III PCMCIA slot. This slot can be used with flash cards (or hard disks!) to extend the recording time, but the slot can also take communication cards that are then used for file transfer (more on that later). The side of the battery pack is also visible on the left hand side of the image - it goes all the way along the back of the recorder.

On the right hand side of the case the analogue audio connectors live as well as the power input. The outputs are professional line-level balanced outputs. The inputs can be switched between line and microphone, using the built-in mic pre-amp. For microphones there is also the option of switching on 12V or 48V phantom power (which most pro-audio microphones require). There is also a rumble-filter, which is a filter that removes low-frequency noise like the handling of the microphone. Each of these options can be switched on and off via small switches on the top of the unit, independently for each channel.

At the bottom left of the image the headphone socket is visible. The top of the unit also features a small grille behind which a speaker sits.

The result (functionality)

Rather than going through the full list of functions, which would be long and tedious, this section highlights a couple of things that were quite unique to this recorder.

Editing

During the design phase there was a change in management, which caused the requirement for audio editing to be added to the feature list. This was at quite a late stage of the development and happened after the development team had committed the hardware and case design. Adding a jog wheel and changing the chipset to allow for scrub editing was out of the question unfortunately. However, the custom made display did have quite a large graphical section and that allowed a representation of the waveform to be shown. This in turn then allowed the unit to have graphical editing as shown in the photo below:

While the unit is recording the user can press the "Mark" button to place a time marker. In the editor these markers are shown with single dots under the waveform. A line under the audio represents a selection, which can then be cut out or copied and inserted into another location in the same recording, or even edited into a different recording.

Just like with the Digicorder all editing is non-destructive and allows for easy undo functionality. The edit is stored as if it was a separate recording. This is done to ensure that the original recording and the edit are both always directly accessible and makes creating multiple edits from the same recording easy. Edits of edits are of course also possible.

Recording

Apart from recording everything from the moment the record button is pressed until the stop button is pressed there are also two additional recording modes that are designed to limit the amount of the expensive storage used.

The first is "Timeshift" recording, during which the Easycorder captures all audio to an internal buffer of N seconds. The user can specify N to be anything between 20 and 60 seconds. When the buffer is full any new audio added will cause the older audio to be removed so that the buffer always contains the last N seconds of audio captured. As soon as the recording button is pressed again the audio in the buffer is stored at the start of a new file and the recorder keeps recording to the file until the stop button is pressed. The result is that the recorded file can actually start up to N seconds earlier than the record button was pressed. This makes missing the start of a chaotic press conference a thing of the past.

The second is "Smart space" recording. This mode starts the recording when there is audio detected and stops the recording when there has been no audio detected for a while. This limits the amount of storage space wasted on silence or low-level audio.

File transfer

For a radio station to be able to use the recorded audio it needs to be "imported" into their automation system. This is achieved with a Windows program called "EasyCollector" that can receive the audio in a number of different ways.

Use a flash card in the external card slot of the Easycorder to copy the recordings from the internal storage. Then eject the flash card and put it in the PCMCIA card reader of the PC. This requires the PC to have a PCMCIA card reader installed.
The Easycorder has an extended capability parallel port that can be used to transfer files over to the PC. This is not particularly fast, but is still considerably faster than playing audio over in real-time as with tape and cassette recorders.
Using a PCMCIA modem card in the external slot of the Easycorder allows it to connect over a standard analogue telephone line to the modem of the EasyCollector PC. This requires a phone line as well as a modem at the PC end.
Using a PCMCIA ISDN card in the external slot of the Easycorder allows it to connect over the ISDN network to the EasyCollector PC. This requires an ISDN line as well as an ISDN terminal adapter to have been installed in the PC.

The last two options allow the user of the Easycorder to transfer the recorded audio back to base without having to physically travel there. Nowadays we would use the Internet for that, but in those days access to the Internet was either via dial-up or via ISDN, which made using dial-up/ISDN to connect to base directly much more efficient.

Live audio

Now that we had gone full circle with the Easycorder and implemented a lot of things that were not planned at the beginning, we (the five design engineers) were wondering if we could get the Easycorder to do live real-time audio over ISDN by using an ISDN card in the external PCMCIA slot. As I had most experience with this (I implemented this same thing previously for the Digicorder) it was up to me to have a go at it, but with help of the other engineers as well of course. I remember a chat with a hardware colleague who suggested mixing some audio sources in the CPLD and promptly came up with the goods.

In the end the functionality allowed for a live broadcast quality audio connection over ISDN, including the option to play back recordings while being live on air. The only downside was that the recording had to be made with the same audio compression settings as the ISDN connection was using. A slight hack allowed the user to hear themselves in one ear of their headphones and the sound of the remote side of the connection in the other ear.

Concluding

The Easycorder was introduced at the 1997 International Broadcasting Convention in Amsterdam. It was still a current product when I left the company early 2000 so I'm not entirely sure at what point it was removed from sale. I do know that its successor, the Maycom Handheld recorder, had already been worked on for about a year by then.

Additional information

Part of my old archive of Maycom artefacts is a number of sales brochures and magazine articles from that period. I have scanned some of these and provided the links to PDFs of these scans below:

Easycorder Classic (6MB) - An early brochure showing the Easycorder Classic.
Easycorder Sport (6MB) - A later style brochure showing the Easycorder Sport.
Audio Media article (6MB) - An article about the Easycorder in Audio Media magazine.
What's news 4 (4MB) - Exhibition hand-out showcasing the Easycorder.

Classic AmigaOS Programming: The Network

Wed, 26 Mar 2025 19:00:57 +0000

Paperback now available on Amazon.

The third book in my "Classic Amiga Programming" series has just been published. This took a bit longer than anticipated due to my BassMX project (for which I'm still building units) being more popular than I anticipated.

My previous two books concentrated mainly on using the functionality provided by the Amiga's chipset and by AmigaOS, this new book is about adding network and Internet functionality to Amiga programs.

The Blurb

"The number of Amigas with a network connection has been growing steadily. This is in no small part helped by projects like PiStorm and Plipbox that add a network device that can be used by any Amiga network stack. At the same time projects like AmiSSL allow the Amiga to use current encryption standards to securely connect over the Internet. More and more people being able to connect their Amiga to the Internet means that adding a networking option to games and other software is no longer serving just a small number of users.

This book is aimed at coders who are familiar with creating software for the OS of the classic Amiga but have no experience with using the network and the Internet in their programs. The book assumes that there already is a working Internet connection on the Amiga. For Amigas that are emulated with WinUAE there is a short appendix that shows how to enable the built-in network stack of WinUAE.

This book consists of four parts. The first part dives into how the network works, explaining the basics of addressing, routing and the IP protocol. This is followed by the part about network programming using sockets on the Amiga, which includes examples in C as well as in assembly language. The third part acts as a primer on encryption, concentrating mainly on how this is used by SSL/TLS. The book's last part shows how to use the AmiSSL library to create encrypted connections on the Amiga, again with examples in C and assembly.

The C examples can be cross-compiled with GCC or even compiled natively with VBCC. The assembly examples have been tested with Asm-Pro as well as HiSoft DevPac."

I have provided the table of contents as a download here.