Just a quick update.
There is something off with the firmware that was unpacked from the midi files earlier in this thread.
Decompilation was very scrappy and needed lots of manual intervention when it should not have required it.
As a test, I ran the firmware from a Nissan ECU (it uses the same CPU) through the decompilation and boom, a screen full of sub routines and jumps to them.
I don't get that with either the SP808 firmware or the A6 firmware.
Next, I'm seeing patterns in the firmware I wouldn't expect.
I'm seeing
Code:
7F 00 00 00 00
repeated every 14 bytes. And other anomalies that repeat through the code, suggesting it's an artifact of the midi extraction.
The other thing that makes no sense, the A6 firmware is bigger than the SP808 firmware??
I'd expect the SP808 firmware to be bigger because it has all of the effects and Synthesis that the A6 doesn't.
Very odd.
Current plan is to dump firmware to disk and examine that. However, I have just ordered a chip programmer that can handle the 56 pin flash chip, and that will be my next port.
Finally, I'm going to see if the UART on CN7 yields anything useful, as there are some strings in the firmware that are never shown on screen or stored on disk.
HSIBOY