WIP/RFC: Add support for the Texas Instruments Tiva TM4C123GLX ARM Cortex-M4F MCU

[benpicco]

This adds basic support for the TI TM4C123GH6PM MCU and the TM4C123GLX Launchpad development board based on it.

TM4C123GH6PM is a Cortex-M4F based chip with 32kiB Ram, running at up to 80 MHz.
As a special feature it provides 'ROM Functions', similar to BIOS calls, that are always present on the chip and that can be called using a memory table.

There are 6 32 bit general purpose timers and 6 64 bit general purpose timers.
Timers can be 'split' into two half-with timers (16/32bit). Prescaler is only available in half-with mode when counting down, when counting up it will extend the range by 8 bit.

There is also a currently unused 24 bit SysTick timer (also with no prescaling, only variable interrupt periods within the 24bit range)

I used stm32f4 as a template for this port.

working so far:

• UART (tx only)
• timers (32bit timers in full width mode are exported through hwtimer, no prescaler), tests/vtimer_msg crashes after ~53s

Depends on #1709 to run properly

[LudwigKnuepfer]

cpu/tm4c123/syscalls.c:92: style (unsignedLessThanZero): Checking if unsigned variable 'incr' is less than zero.

[Kijewski]

Where is the signature from? It should be void *_sbrk_r(struct _reent *ptr, ptrdiff_t incr);

[LudwigKnuepfer]

file has an unknown license header: 'cpu/tm4c123/include/tm4c123gh6pm.h'

[benpicco]

gnaa, I missed that!
Now that sucks quite a bit. I asked in the TI forum if the licence for the CMSIS header is really meant to be that way, but I'm afraid they are not going to change that.

That would mean I can't use cortex-m4_common or at least I'd have to fork it so it uses TivaWare headers instead of standard CMSIS :(

[miri64]

I'm not an expert (and as we all no: sentences that start like this are not really constructive) but I highly dought, that a bunch of type definitions is licensable. In case of doubt: just change the names ;-P

[LudwigKnuepfer]

@haukepetersen your input on CMSIS here ;)

[thomaseichinger]

maybe #1697 with this file could be of interest in this context.

[haukepetersen]

Hm, that license reads rather restrictive... What we did earlier with some STM standard lib was to include it only as external pkg in RIOT, so we didn't include the files in question directly into RIOT. The nicest solution would actually be to write CMSIS-style headers for TI MCUs ourself, but that would be a shitload of work... I'm not sure of the best solution in this case here...

[OlegHahm]

How do we proceed with this one?

[jnohlgard]

@benpicco Are there any .svd files available for the MCU under a different license? It should be possible to auto-generate the CMSIS style headers from those.

[OlegHahm]

@benpicco, ping!?

[benpicco]

The only .svd files I could find came with the very CMSIS headers (TI forum)

An option would be to use TI driverlib instead of CMSIS and create a tiva-c architecture as TI did for Contiki - but I'm currently not working on this, so you might as well close this pull request.

[jnohlgard]

Closed upon request. Open a new PR if we find any license-compatible headers that we can use.

[tmick0]

Is anybody still working on this? I had forked benpicco's work myself and got some basic functionality up on the EK-TM4C1294XL. But now I'm thinking about downgrading to the TM4C123G for my project, and I'm curious whether I will be able to use it with a more recent RIOT than 2014.12...