swd_module

Introduction

A kernel module to program Cortex-M MCU by emulating ARM Serial Wire Debug (SWD) protocol.

• Some SoCs like raspberry-pi which has powerful application core running Linux kernel but no real-time processing unit.
• Some MPUs like AM33x used by Beaglebone-Black has a PRU and STM32MP1x has a cortex-m core.
• This kernel module aims to make the SoC which has no sub-core have an external extended cortex-m sub-core and control it by SoC via emulated SWD protocol.

Wiring

Please refer this figure for the wiring

Usage

swd

• Set the _swclk_pin and _swdio_pin.
• Set the core
• compile
• use (Please refere to the test cases)

rpu_sysfs

Structure of rpu_sysfs "/sys/class/swd/rpu"

/sys/class/swd/rpu
├── core_name  // core name
├── core_mem // mem info/layout of core
├── control // control the core to be halt or unhalt
├── flash   // read/write on flash
├── ram     // read/write on ram
└── status  // check the core is halt or unhalt

• halt core by "$ echo 0 > /sys/class/swd/rpu/control"
• do read/write on ram/flash. i.e. "$ cat blink_$corename.bin > /sys/class/swd/rpu/flash"
• unhalt core by "$ echo 1 > /sys/class/swd/rpu/control"

stm32f103c8t6(bluepill)

Verified function and SBC boards of swd

	Reset line	Test Alive	Read IDCODE	Write to RAM	Read from RAM	Write to Flash	Read from Flash	Erase entire Flash
RPI3-B+
RPI4

Verified function and SBC boards of rpu_sysfs

	Core halt	Core unhalt	Write to RAM	Read from RAM	Write to Flash	Read from Flash
RPI3-B+
RPI4

stm32f411ceu6(blackpill)

Verified function and SBC boards of swd

	Reset line	Test Alive	Read IDCODE	Write to RAM	Read from RAM	Write to Flash	Read from Flash	Erase entire Flash
RPI3-B+
RPI4

Verified function and SBC boards of rpu_sysfs

	Core halt	Core unhalt	Write to RAM	Read from RAM	Write to Flash	Read from Flash
RPI3-B+
RPI4

Build Instruction

Prepare Environment

• rpi kernel header

$ sudo apt update
$ sudo apt install raspberrypi-kernel-headers

• gcc, make, git

Clone Code

$ git clone https://github.com/Nothing-Lt/swd_module.git --recursive

Build swd_module

$ cd swd_module/src
$ make

• Install swd_module

$ sudo insmod swd.ko
$ sudo dtoverlay swd-device-overlay.dtbo

Build test program

Test program for rpu and swd are preapred

swd

$ cd swd_module/test/swd
$ make
$ run_test.sh stm32f103c8t6 #or stm32f411ceu6

rpu

$ cd swd_module/test/rpu
$ make
$ run_test.sh