board:cpu: RIOT port for the atsamr21xpro board

[thomaseichinger]

List to coordinate porting efforts for the samr21xpro board and it's samd21 cpu.
Please leave a comment what you are working on to mark it in the list and
open pull requests against https://github.com/thomaseichinger/RIOT/tree/samr21 master branch.

Porting todos:

• basic file structure @thomaseichinger
• cortex-m0_common usage @thomaseichinger
• scripts for flashing/debuging (needs newest openocd from git) @thomaseichinger
• LED marcos @thomaseichinger
• set F_CPU correctly
• LPM - under review cpu/samd21: implement low power modes #2309 @LudwigOrtmann @saurabh984 (cpu has periph/pm)
• peripheral drivers
  • UART @thomaseichinger, @Troels51
  • timer @thomaseichinger, @Troels51
  • GPIO @Troels51, @thomaseichinger
  • cpuid @wiredsource
  • SPI @Troels51
  • I2C @bapclenet
  • rtt @daniel-k cpu/samd21: Add RTT driver #2918
  • rtc @bapclenet
  • pwm cpu/samd21: Add samd21 pwm driver #2473 cpu/samd21: added peripheral PWM driver #3127 @haukepetersen
  • adc - under review Samr21: ADC implementation #2063 @wiredsource SAMR21 [ADC] #4162 @msolters Done in SAMD21/SAMR21: Add more ADC lines #7009
  • random number generator (RNG) (at86rf2xx: at86rf2xx_get_random to at86rf2xx_internal for supporting boards #4989)
  • PLL @haukepetersen cpu/samd21: added cpu clock configuration code #3034
• radio driver, done, at86rf2xx @haukepetersen (at86rf231 driver works for now, will get at86rf2xx) @thomaseichinger @Troels51
• wiki documentation @haukepetersen

[N8Fear]

Sorry - I should really look where I'm clicking at... :-/

[Troels51]

Hey, i'm new to this project but i'm looking into porting RIOT to the board as well.
I've been working on gpio and timers

[thomaseichinger]

@Troels51, welcome! Great to hear, I marked GPIO in the list with your name.

[wiredsource]

@thomaseichinger
Troels and myself are two of the tree students from Aarhus University.
e.g. "[riot-devel] RIOT OS for the Atmel SAM R21 (ARM m0+)" thread

[thomaseichinger]

@wiredsource welcome to you too! Are you working on GPIO too?

To give a short update regarding UART, I've some output right now but it is still invalid.
Also watch out when configuring GCLK modules, if misconfigured the board isn't reachable
anymore via open-ocd and has to be erased using AtmelStudio (AFAIK Windows only).

[wiredsource]

@thomaseichinger
Right now i'm just spectating because i need a better overview over the system. @Troels51 has worked with it for the past week so he has a way better understanding of the architecture.

I will start on something constructive soon :-)