Hi all, I’m having some issues with my newly assembled MK312-BT (PCB v1.3R) and hope someone can help. I can compile the firmware from the buttshock-et312-firmware Github repository fine, and flashed m005 to my board. The first line of characters on the display are all white (I picked a different color display) and the second line is all dark. The OUTA and OUTB lights flash slowly. I tried again with f005 and had the same result. I am using the LTC1661 DAC.
Then I tried flashing the original 312-16-decrypted.bin firmware. I see “Failure 20 Shut Off Power!!” on the display and the OUTA and OUTB lights flash, faster than when using the m005 or f005 patched firmware. Of course this original firmware requires the MAX548 DAC, so I switched the DACs on the board. Same result. Using the MAX548 and following some of the debug steps I found here, I observe a similar problem as observed by Cerb in post 8 in the same thread.
I see 9V at the drain of each MOS device and observe a 5V, 500us pulse on PB2 and PB3 at power up. Oddly enough, PB0 and PB1 show junk similar to what is observed in that thread. Different looking junk, but junk all the same. I then observe a 2V, ~500us pulse across the sense resistor R30 on power up.
Here is a scope screenshot of the pulse I see on PB2 (it’s the same on PB3). Excuse the scale, I did measure it to be 500us.
Here is a scope screenshot of the pulse I see on PB0. It’s the same as what I observe on PB1.
Here is a scope screenshot of the pulse I see across sense resistor R30.
Any suggestions as to what could be the problem, and what I should consider suspect on the board for further debugging?