1 UART Connection

Any UART to USB adapter should work. We use an FT4232H adapter that is available from distributors for around 28€. You require a USB-A to USB-Mini-B cable to connect the FT4232H to your computer and 3 dupont cables to connect the FT4232H to the AXIOM Remote.

1.1 FT4232H Pinout

FT4232H.jpg FT4232H-pinout.jpg

Chip Datasheet: https://ftdichip.com/wp-content/uploads/2020/08/DS_FT4232H.pdf

Mini Module Datasheet: https://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_FT4232H_Mini_Module.pdf

1.2 FT4232H wiring

FT4232H features 4 UART ports, in this example we utilize port C. Under Linux the FT4232H should simply show up as ports /dev/ttyUSB0 to /dev/ttyUSB3 where port C from the above example would correspond to /dev/ttyUSB2.

Note that the Transmit (TXD) and Receive (RCD) lines need to be cross wired meaning TXD needs to be connected to RXD and RXD to TXD. You can choose any GND pin though.

Name FT4232H pin Remote pin
GND GND GND
TXD CD0 RXD
RXD CD1 TXD

Axiom-remote-uart-pins.jpg FT4232H-pinout-uart-portc.jpg

2 JTAG connection

2.1 FT4232H wiring

5 dupont cables are required to hook up JTAG to the FT4232H.

Name FT4232H pin Remote pin
GND GND GND
TCK AD0 TCK
TDI AD1 TDI
TDO AD2 TDO
TMS AD3 TMS

Jtag.png FT4232H-jtag.jpg FT4232H-jtag-pinout.jpg Jtag-ft4232h-pinout.jpg Remote-jtag-adapter.jpg

2.2 Flashing

It is possible to flash the PIC32 firmware through pic32prog and FT2232H and FT4232H adapters (amongst others, like PICkit3). Multiple devices which use FT2232H are already supported in pic32prog, but not FT4232H. We've forked pic32prog, added FT4232H support and adjusted the build to reduce problems there.

https://github.com/apertus-open-source-cinema/pic32prog

Usage example:

./pic32prog -s 1500 -S AXIOM_Remote_Firmware_635.hex

Output:

Programmer for Microchip PIC32 microcontrollers, Version 2.0.258
    Copyright: (C) 2011-2015 Serge Vakulenko
      IDCODE=5510e053
      Adapter: Generic FT4232H adapter
    Processor: MZ2048ECG100
 Flash memory: 2048 kbytes
  Boot memory: 80 kbytes
         Data: 135904 bytes
        Erase: .......done
Program flash: ################################## done
 Program boot: ### done      
 Program rate: 35484 bytes per second

Note: Don't forget to press reset button after flashing, as by default reset (MCLR) will be hold by the programmer.

2.3 Debugging

Our tests with OpenOCD and FT4232H were only partially successful, PIC32 could be accessed, resetted and halted, also registers and disassembled code inspected, but breakpoints could not be set properly or were not stopping the execution. Luckily there is a tool called ejtagproxy, which can be used instead of OpenOCD. Also the connection from gdb-multiarch is working properly and breakpoints are stopping the execution.

ejtagproxy supports same devices as pic32prog. We've forked ejtagproxy' too and added FT4232H support.

https://github.com/apertus-open-source-cinema/ejtagproxy

Note: Use gdb-multiarch which is able to debug MIPS targets.

Start ejtagproxy:

./ejtagproxy

Output:

GDB proxy for Microchip PIC32 processors, Version 1.0.36
Copyright (C) 2012 Serge Vakulenko

EJTAGproxy comes with ABSOLUTELY NO WARRANTY; for details
use '--warranty' option. This is Open Source software. You are
welcome to redistribute it under certain conditions. Use the
'--copying' option for details.

ejtagproxy: waiting on TCP port 2000

Start gdb-multiarch':

gdb-multiarch

Connect to ejtagproxy:

target extended-remote localhost:2000

or

tar ext :2000

Load symbol file (to see the names of function where the target was halted, instead of addresses, and to be able to set breakpoints via names and not only addresses):

file <path to .elf file>

Example

file /home/dev/Projects/Firmware/build/AXIOM_Remote_Firmware_635.elf

Some useful commands:

Command Short form Description
reset r Reset target (PIC32)
CTRL+C Halt the target
continue c Resume execution after halt
break PollButtons b PollButtons Set breakpoint on function PollButtons
break 0x9d001f73 b 0x9d001f73 Set breakpoint on address 0x9d001f73
info breakpoints i b Show set breakpoints
delete del or d Delete all breakpoints
delete breakpoint 3 del 3 or d 3 Delete breakpoint 3, see 'info breakpoints'
info registers i r Show available registers and their values

2.3.1 Debugging in VSCode

TODO