Here are some photos of my modified PSIM module built in MOTM format. The original Synthmodules.com site is gone but you can still find parts of it on the internet archive. The Yahoo group still exists but has not had a related posting since 2008. (I don't believe Brice Hornback ever finished and shipped last 9 modules and I volunteered several times that I would complete them if he would send me what parts he had. Alas I could never maintain reliable contact with him.)
The original PSIM was a Frac module with simply four analog inputs and outputs, three digitial channels with switches, and 6 LEDs. I expanded my PSIM module wth MIDI input, MIDI output, SpeakJet, and CV controls normalled to a +10 volt reference for each of the input channels. Later I added a 1U companion LCD display. This became the inspiration for my open source 8 channel precision ComputerVoltageSource module.
I combined switches for the PSIM and SpeakJet. Up (blue legends) control the SpeakJet and down control the PSIM. I upgraded my SpeakJet interface from the original software controlled serial interface to an I2C interface with a TTS256 to make programming easier and compatible with interrupts. This photo shows the original SpeakJet interface on the left. The +5 volt regulator for the PSIM has been folded down with a heat sink to lower the case temperature. The MIDI input and output module is barely visible in the middle with the cv controls.
MOTM-format PSIM FrontPanelExpress design file
MIDI input and output schematic
More information and photos of the SpeakJet implementation
More information and photos of an analog/digital expansion for the PSIM
I got a surplus 2x20 vacuum fluorescent display module from Noritake Itron which supports scrolling, four brightness levels, and user-definable fonts. It interfaces with parallel or serial up to 9600 baud. I used the PSIM Aux for serial output to the display but the two 10K series resistors limited the current so I had to buffer it with a single transistor. I had to use the software serial command which is not compatible with interrupts.
A follow-on project to this VFD display was my External LCD module. This significantly reduced power from the 400 mA that the vacuum fluorescent display requires. I changed the interface to the display to use a MIDI sysex command which eliminated the Aux output issues of current and interrupts. I built a similar version into a 1U PSIM Display module using a 2 line x 8 character LCD display. I modified this design for the ComputerVoltageSource LCD and now use this as my standard display. I use the display for program names and to indicate control selections, modes, and input and output voltages. Programs that used the smaller 2 line x 8 character LCD just utilize the top line of the 2 line x 16 character LCD.
All of my operational and verification/calibration programs have been moved to my Programs page. I have also documented a number of hardware and software details for the AtomPro24 and AtomPro28 in my AtomPro FAQ updated