MK312BT Failure Modes 20 and 21


My 312BT build is now complete but am getting Failure mode reports on powering up
Mode 20 with just the battery connected (battery is charged and meter shows about 14V)
Mode 20 with both battery and mains connected
Mode 21 with just the mains power supply connected (PSU is the RS 18V one in the build list)

My question is does anyone know what sort of test the code is doing on startup to check the voltages on the board and then where should I stick the meter along the path from the battery to the ATMEGA to check each step of the way and what voltages I should expect - a circuit diagram would really help :slight_smile:
I did get the box to boot once when put a 12V power supply across the battery inputs but have not been able to repeat this so something is very close to tolerance somewhere


If you haven’t figured this out yet, see this thread: MK-312BT Failure 20


Thanks will do - I think it gives me a lot of clues
I’d still really like to know what actually triggers mode 20 in the code


Check the values of the resistors.
Check the orientation of the transformers


BTW, if you’re wondering about the difference between error codes… I kinda forgot we documented that back during the et312 firmware reversing process. >.>