It is possible to erase, reprogram and debug software running on a Tesla Model 3 / Y drive unit inverter using a simple JTAG adapter. No additional hardware, software or knowledge is required beyond TI Code Composer Studio and a JTAG adapter. Erasing the flash on the device will remove code protection applied by Tesla allowing the device to be re-used.
Disclaimer: Building and using a JTAG adapter as described here can wipe existing firmware from your Tesla inverter rendering it completely non-functional. Doing this is at your own risk.
An easy to use JTAG adapter specifically designed to fit the Tesla M3 inverter has been built by Damien Maguire. This can be purchased from his shop.
A simple adapter can be made with an FTDI FT2232H-56Q MINI MODULE, a Hirose DF20A-10DS-1C connector shell, Hirose DF20F-2830SCFA connector pins and some 30 AWG wire-wrap wire. The crimps pins are incredibly small and fiddly to assemble.
| FTDI FT2232H | Pin | Tesla JTAG | Pin |
|---|---|---|---|
| ADBUS0 | CN2-8 | TCK | 9 |
| ADBUS1 | CN2-9 | TDI | 3 |
| ADBUS4 | CN2-13 | /TRST | 1 |
| ADBUS2 | CN2-10 | TDO | 10 |
| ADBUS3 | CN2-11 | TMS | 4 |
| GND | CN2-1 | GND | 5 |
Also connect ACBUS5 (CN2-23) to GND (CN2-3) with a 1K resistor. Failure to do this will mean that Code Composer Studio will fail to connect to the target device.
The full JTAG pinout is available: https://github.com/damienmaguire/Tesla-Model-3-Drive-Unit/blob/master/M3_TMS_JTAG_Pinout.pdf
Once assembled the FTDI FT2232H must be programmed with the correct USB identifiers and configuration so that it appears to the host PC as a TI XDS100v2 JTAG adapter. To do this use the Windows FT_PROG to apply the TI template.