CMSIS RTOS with nRF51822 and S110

[Mike Thomspon]

I'm looking into using the CMSIS RTOS on the nRF51822 with the S110 softdevice which I've used successfully with other Cortex M0 MCUs. I realize the S110 isn't well tested with various RTOS, but documentation indicates it should be possible.

When initializing the softdevice stack with the call to sd_softdevice_enable(), the return code is 0x0D which nrf_error.h indicates is NRF_ERROR_TIMEOUT. However, the documentation for this function in the header files doesn't indicated this is an expected error to be returned. I'm assuming there is some sort of conflict between the RTOS and the softdevice, but it's unclear what the nature of the timeout might be.

Any hints on where I can look to track down the cause of this issue?

Also, if I get the above issue worked out I'm a bit worried about a conflict between the SVC handling by the softdevice and the RTOS. Since the softdevice controls the SVC interrupt handler, I'm assuming it properly chains the SVC calls intended for the RTOS use. Or, is this a bad assumption on my part.

Thanks,

Mike

[Mike Thomspon]

Another update. I've figured out that I'm calling sd_softdevice_enable() from the initial RTOS thread and it's running off the process stack pointer (PSP) when it calls into the function via the SVC interrupt. The softdevice handler, however, assumes the thread was running off the main stack pointer (MSP) and uses the MSP to extract the SVC number -- which of course is wrong as it's on the PSP stack.

It seems the softdevice SVC_Handler should determine which stack was being used when the SVC interrupt was called as it could then correctly pull the SVC number off the correct stack. I'll have to investigate further regarding what the work around for this issue might be.

[Ole Morten]

This is actually most likely spot on. There have been fixes to S110 version 6.0.0 to fix its stack pointer use, and I believe this should solve your problem. What threw me of was actually the weird return code you got, since I've seen other things causing that previously. I will however have a go at your project now and see if I can get things running.

[Paul]

Hi Mike I was in exactly the same shoe you are last April. I traced right into the assembly too. There was no solution from Nordic that time. So I modified the RTOS source and recompiled the CM lib, which fix the stack problem. I got the latest silicon a couple of weeks ago. I haven't got a chance to verify this issue yet. Do you have any updates? Paul

[Mike Thomspon]

With limited testing, it appears that the S110 version 6.0.0 will work successfully with the Keil CMSIS RTOS for our purposes. To get things working I had to substitute RTC1 for SysTick which unfortunately is not on the nRF51 silicon. This in turn caused a conflict with the Nordic timer library which also uses RTC1. I had to rework the ble_conn_params.c library to use the CMSIS RTOS timers because of this, but it wasn't too much work. With these changes things have been working pretty well for us and being able to use threading on the nRF51 will make our application development easier.

[Paul]

I tested S210 V2.0.0 and V3.0.0 side by side. V3.0.0 won.:-D