Posted by KarlP on 3 May, 2012
A while ago I put together a C driver for the MRF24J40 802.15.4 modules from microchip. I had been using them as a cheap alternative to xbees in some AVR projects. As I’ve been moving on to STM32 parts for hobby projects, (more power, cheaper) I started off porting my driver code from AVR over to cortex m3.
This has been quite an experience. The arm toolchain experience, and particularly the libc support and general documentation is completely different to, say, avr-libc (AVR-libc is a great project, reallly solid)
However, with lots of learning, and lots of mistakes, I’ve got it all working. It’s a first cut, but the basic features are there. There’s no magic for DMA, and you have to do a lot of the pin setup yourself, but this is Cortex M3, there’s so many pins you could be using for this! I’ve tried to reduce the required function calls as much as possible, but there’s still room for improvement.
// Required by the user code
extern void mrf_select(void); // Chip select, if necessary
extern void mrf_deselect(void); // chip deselect, if necessary
extern uint8_t spi_tx(uint8_t cData);
extern void _delay_ms(int); // only used at init time.
This still needs to move to a clear sub project, currently it’s a separate code base to the AVR code.
Get the code now!
More to come, as it gets tidied up and put into use!
Posted by KarlP on 8 November, 2011
I’ve been hacking a lot on STM32 based microcontrollers recently. Not on any particularly useful code, but trying to make the support for the STLink v1 and STLink v2 SWD debuggers built into the various Discovery boards that ST makes really rock solid. It’s a bit of a battle, but it’s coming along
One of the things that has been causing some problems is the sheer volume of information spread across all the different datasheets and release notes. This is going to be particularly apparent as I try to fix the flash programming. Anyway, this afternoon I mapped out the relations between all the datasheets, and put them in a table that I think should help…. (This is based on latest datasheets as of today, some of the numbers changed recently)
The very very very rough version of the map is available here The html is disgusting, blame open office. The spreadsheet it came from is here too:
STM32 Datasheet map
Posted by KarlP on 20 June, 2011
I’ve been increasingly intrigued by the plummeting price of ARM cortex-M3 devices, both the chips themselves, and also some of the development boards. With ST’s newest, the low power STM32L Discovery board, I thought I’d take the plunge, see what could be done. For a few dollars more than the STM32VL Discovery board, you get:
- Twice the RAM
- Lower power consumption
- A touch slider interface
- A nice glass LCD
I only got it today, and given that I run linux at home, it’s a bit of a minefield of toolchains, especially if I want to use neat things like hardware debugging. (One of the sexy things you get when you move up to a “real” CPU) I’m sure I’ll write more as this unfolds slowly, but here’s some first impressions.
The touch slider is neat! The preloaded demo code cycles through a few different modes showing off lower power consumption, but that sort of stuff you could read off the spec sheet. A nice responsive touch slider and a good clear LCD, with a couple of user LEDs and another hard button (The slider can also be used as 4 buttons) makes this a pretty kick arse basic platform!
The screen printing is a bit messy and cluttered, with lots of different sizes. I really don’t know why they felt they need to print the numbers of every resistor and capacitor? It’s a little hard to find which jumper is which. Continuing on cosmetics, why are some jumpers labelled JP, and some labelled CN? Why are some of them on the bottom of the board, and some on top? Odd. Anyway, let’s see if we can get some code on it!