In my prior blog ( Multi-Voice Synthesizer - Part 2 - Voice Module rework. ) I detailed my rework and testing of the Voice Module. In this update I will share my rework of Main Board and bring up of the Echo Module. It has continued to be a struggle to work around the errors that existed in my initial designs, while I attempt to test the various features of this design. There was even smoke!
I have been plagued with connector issues, even in spite of several attempts to line up the pin-outs of the connector, there were several errors. I managed to line up the top and bottom rows of mother board connector, but somehow I flipped the left to right ordering of the pins. This caused me to create yet another adapter board to be built to sit between the mother board and the voice module. Here is a image of the current stack of modules:
All of this rework has shown that my solder skills have some serious limitations. If it is mounting components to a board, I can handle just about anything. But give me a wire to solder to a component lead or trace, and I am going to struggle (and the results will show it). After multiple attempts, I did manage to get everything up and running together. Here are a couple more images of the carnage:
Even with all of the rework, I was eventually able to get the various pieces to play together (pun intended) enough to write some software for each of the modules. This allowed me to tweak and tune some components to bring everything a bit closer to were I wanted to be. To assist in the debugging, I wrote a control panel program (PC) to control the synthesizer functions. Here is a screen shot:
This control panel project was cloned from another project, so it has a few extra controls that I will eventually will remove, but presently it does the job. The very top controls are inactive (except for the CommPort selector). The middle section of the controls allow me to select a waveform, control the attenuation (now Gain), Filter settings and the PWM control for the VCA. Also the Main board mixer gain and the Echo module On/Off, Delay and feedback mix functions. The lower two windows are debug assists, showing the outbound serial and replies. The commands are currently focused on providing low level control to the hardware. Outbound commands are prefixed with either a V or M, targeting either the Voice Module or the Main board (the Echo module is controlled by the Main board).
Here is a short video, taken while I controlled Voice module pitch and waveform, along with the Echo modules delay and mix functions. While I am waiting to design new boards, the VCA and filter functions of the Voice module are no available, so these are not true notes, just pitches.
Going forwards - I have already redesigned my Voice Module, so now I will move over to the Main Board and the Echo Module. I am going to try and see if I can combine these two boards on this round. If the design is to big to fit, I might also try making the Echo Module fit as a dedicated slot (top side) on the Main board. Other than that I want to try some cleanup of power and ground (split digital and analog a bit better).
On the Main board, I want to add a serial EEPROM to hold wave tables that can be sent to the Voice Modules and modify the current Voice Module slots to match the revised Voice Module design. Then I need to figure out where the Echo function end up.
Thanks for reading along!
