Programming secondary chip using SWD interface

[Ofer]

Hi

I have a chip in main board that can be programmed using SWD interface.

1. Can I use the SWD of the STM32F407 to program another chip (and not just for programming and debugging the STM32) ?
2. If so - Are there any HAL functions ?

Thanks

[S.Ma]

Embedding debug probe function is far from simple. Typically bootoader enables reflashing through uart, i2c, spi. Application code on target for in application programming is another way. HAL doesn't provide SWD serial function.

[Ofer]

Hi

I'm sure it is not a simple task, but I might be doing it if it technically possible.

I see in the reference manual: https://www.st.com/resource/en/reference_manual/dm00031020-stm32f405-415-stm32f407-417-stm32f427-437-and-stm32f429-439-advanced-arm-based-32-bit-mcus-stmicroelectronics.pdf

page 1695 a list of registers that may help me doing this task.

Is someone ever did it ?

[Tesla DeLorean]

The SWD protocol on the MCU side is implemented in hardware. It's not designed to host other devices, and is not inherently a software/firmware based method. ie combinational/synchronous logic clocking into the 10's of MHz

[Peter BENSCH]

That would be a kind of daisy chain, but no, unfortunately this is not possible with SWD and there are no functions for it.

Regards

/Peter

[Ofer]

Hi Peter, I'm not sure you understood me correctly.

I'm not trying to program from PC to the STM32 and from then to the other chip.

I'm trying to control the STM32 to program the other chip directly with no other host.

Thanks

[TDK]

Daisy chain or not, it's not supported. The SWD pins are only for programming that device.

You can certainly emulate the SWD protocol using other pins (or even the SWD pins), but that's not a realistic solution and certainly isn't supported in HAL.

[Andrew Neil]

"Can I use the SWD of the STM32F407 to program another chip"

No. The SWD in the microcontroller is a "slave" - it can't be a "master" to another microcontroller.

Have you looked at CMSIS DAP ?

https://os.mbed.com/handbook/CMSIS-DAP

[Ofer]

Thanks to all of you for your answers.

It is not urgent task, but I have to select the pinout to the board.

I will try both options (using the SWD of the STM + using simple GPIOs for bit-banging)

[TDK]

Consider programming the other chip with the bootloader and controlling it with GPIOs connected to the BOOT0 pin, the NRST pin, and the relevant bootloader communication method such as UART. This will be much easier than using SWD.