I added support to run cantact-fw on STM32F072B-DISCO and build files for MDK-ARM/Keil

[trollcop]

Since STM32F072B-DISCO is kinda ubiquitous and can be had for $12 I've added support to run cantact-fw on this board.
An external canbus transceiver breakout can be connected to VDD/PB8/PB9/GND pins on the -DISCO easily. No soldering or modifications needed on the board.

During making the port, I made LED pins configurable, fixed some compile/style warnings and properly fixed running off internal oscillator (072B-DISCO doesn't have a crystal mounted).

I don't have a linklayer board to test with but the changes are pretty simple and should not affect operation on original board.

Oh, and I added build files for MDK-ARM v4, shouldn't hurt anyone I suppose.

[jxltom]

1. It might be better if makefile is also updated based on stm32f072
2. It is also better to update startup_*.s file
3. It will be nice to support two led with different port such as GPIOB and GPIOC

[trollcop]

Allright, I added a new commit taking care of those requests (I don't use gcc/Makefile but I tested both builds and they work).
I'm not sure why its not showing up in the list here but the last commit is here: trollcop@abca338

can be invoked as just make for cantact default, or make BUILD_HW=disco for the -discovery build.

[jxltom]

This is nice.

Just one more thing, maybe it is better to define seperate LED_RED_GPIO_CLK and LED_GREEN_GPIO_CLK to support different ports?

[trollcop]

This is nice.

Just one more thing, maybe it is better to define seperate LED_RED_GPIO_CLK and LED_GREEN_GPIO_CLK to support different ports?

I've left a comment in the PR regarding that - there's no simple way other than duplicating the define, and at the point where a user need to change this they probably know what they're doing. If you have a suggestion of how to implement it better than something like

#define LED_GREEN_GPIO_CLK    __GPIOB_CLK_ENABLE
#define LED_RED_GPIO_CLK    __GPIOB_CLK_ENABLE

I'm all ears, or else it can just be made that way.