Geehy APM32F003 project template

This repository contains my project template (and mandatory LED blinking code example) for the dirt-cheap Geehy APM32F003 microcontroller.

Structure:

• geehy subdirectory contains startup code, linker scripts, CMSIS header files and drivers - all extracted from Geehy APM32F00x_SDK_V1.4.
  • only GPIO and RCM drivers are included in the build, if you need other drivers, you need to edit the Makefile.
• src contains actual blinker source code.

Note:

• I use make as a build tool. I consider reworking it to CMake or SCons some day, to make it cross-platform. Maintaining a cross-platform Makefile is a nightmare (been there, done that), I don't want to fight slashes vs backslashes ever again in my life :) But it's not my priority, though, PRs welcome.
• I've used APM32F003F6P6 (32kB Flash / 4kB RAM) variant, if you want to use APM32F003F4P6 (16kB Flash / 2kB RAM), remember to tweak the Makefile - LD_SCRIPT variable should point to geehy/APM32F00x/Source/gcc/gcc_APM32F00xx4.ld in such case.

Flashing / debugging

I've successfully used a Segger J-Link v8 clone + OpenOCD for flashing and debugging. Support for APM32F00x is not yet included in the official OpenOCD release, however (and Geehy only released Windows binaries, as far I know).

I have found this patch, fixed it to apply cleanly on top of the current code and actually compile, it seems to work fine. You can grab patched OpenOCD from my forked repo, from the apm32 branch (you have to compile it yourself, of course).

For J-Link probe you can use openocd.cfg directly:

$ openocd -f openocd.cfg

For other probes tweak the first commandi in the openocd.cfg file accordingly.

How to run Blinky

In order to build the sample project:

• set ARM_TOOLCHAIN_PATH environment variable to point to the directory containing arm-none-eabi-gcc and other binaries, or set your PATH accordingly (on Ubuntu you can just apt-get install gcc-arm-none-eabi gdb-multiarch).
• run make - if all is OK, you should get out/blinky.elf file.
• flash it to your test board, e.g. with OpenOCD and gdb, issuing load command in gdb.

Test hardware

All my test were performed with a bare minimum circuit done on the breadboard.

The only necessary connections are:

• +5V to VDD (pin 9), ground to VSS (pin 7), some decoupling capacitor
• 1uF capacitor between VCAP (pin 8) and ground
• LED (with 1k resistor in series), between PD4 (pin 1) and ground
• your SWD probe of choice attached to SWCLK (pin 19), SWDIO (pin 18) and NRST (pin 4).

WARNING: the capacitor between VCAP and ground is very important. I've lost a few hours debugging random Hard Fault crashes early in startup code, just to realize that I connected the capacitor to the wrong pin by mistake. On the other hand, demo board from Geehy uses 10k pull-up resistor on SWDIO and 10k pull-down on SWCLK, but everything works fine for me without those resistors.