Test development using CLI/python/RTT

[Tim Adu]

Hi,

I'd like to start developing automated tests for my custom NRF52840 board.

Currently I use the CLI library (with RTT backend) for communicating with the board.

Any ideas for how I could communicate with my board via a python script?

Thanks

Tim

[Jørgen Holmefjord]

Hi Tim,

If you want to continue using CLI over RTT for your communication with the board, you can look into our pynrfjprog library. This enables you to read and write RTT channels from a python script.

Best regards,
Jørgen

[Jørgen Holmefjord]

1. RTT supports mulitple channels. If you want to keep logging, use another channel than 0 for the test communications.
2. Yes, this makes sense to me.

[Tim Adu]

What does it take to use a different channel? I just read this post: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/multiple-channels-in-rtt

Does it paint the full picture?

[Tim Adu]

Okay, so I tried using Channel 1 (both in my python script and firmware), Everytime I run the script, I hit a breakpoint in the code. Specifically, this breakpoint (in cmsis_gcc.h) is hit everytime I send a string from the script:

__attribute__((always_inline)) __STATIC_INLINE void __SEV(void)
{
  __ASM volatile ("sev");
}

And the program halts. Is this expected?

[Jørgen Holmefjord]

I have not experienced this. I did a test with a modified peripheral example, and a custom pynrfjprog sample. This seems to work as expected.

rtt_writer_sdk_16.0.0.zip

Fullscreen rtt_reader.py Download

from __future__ import print_function

# Import pynrfjprog API module
from pynrfjprog import LowLevel
from time import sleep


def run(snr=None):
    """
    Run example script.

    @param (optional) int snr: Specify serial number of DK to run example on.
    """
    print('# RTT read example using pynrfjprog started...')
    
    # Detect the device family of your device. Initialize an API object with UNKNOWN family and read the device's family. This step is performed so this example can be run in all devices without customer input.
    print('# Opening API with device family UNKNOWN, reading the device family.')
    with LowLevel.API(LowLevel.DeviceFamily.UNKNOWN) as api:            # Using with construction so there is no need to open or close the API class.
        if snr is not None:
            api.connect_to_emu_with_snr(snr)
        else:
            api.connect_to_emu_without_snr()
        device_family = api.read_device_family()
    
    # Initialize an API object with the target family. This will load nrfjprog.dll with the proper target family.
    api = LowLevel.API(device_family)
    
    # Open the loaded DLL and connect to an emulator probe. If several are connected a pop up will appear.
    api.open()
    try:

        if snr is not None:
            api.connect_to_emu_with_snr(snr)
        else:
            api.connect_to_emu_without_snr()

        # Erase all the flash of the device.
        print('Starting RTT.')
        api.rtt_start()
		
		# rtt_start() API is non-blocking, need to wait for the control block to be found
        while(api.rtt_is_control_block_found() != True): 
			print("waiting for control block")
			sleep(0.1)

        channel_count_down, channel_count_up = api.rtt_read_channel_count()
        print("Found {} down channels and {} up channels".format(channel_count_down, channel_count_up))
		
        rtt_string = {}
        for i in range(channel_count_down):
			rtt_string[str(i)] = b''
		
        while(True):
			for i in range(channel_count_down):
				r = api.rtt_read(i, 1)
				if(len(r) != 0):
					if(r == b'\n'):
						print(rtt_string[str(i)])
						rtt_string[str(i)] = b''
					else:
						rtt_string[str(i)] = rtt_string[str(i)] + r
        
        api.close()

        print('# Example done...')

    except LowLevel.APIError:
        api.close()
        raise
    
 
if __name__ == '__main__':
    run()

Did you SEGGER_RTT_CONFIG_MAX_NUM_UP_BUFFERS/SEGGER_RTT_CONFIG_MAX_NUM_DOWN_BUFFERS in your sdk_config.h file?

[Tim Adu]

Thanks, I'll give this a try.

In the meantime I noticed that the script you sent primarily does RTT reading, and the firmware does RTT write. Is the reverse possible (writing using the script, and reading using the firmware)?

[Jørgen Holmefjord]

Yes, that should work similarly. I updated the examples with read in application and write in Python script:

rtt_reader_writer_sdk_16.0.0.zip

Fullscreen rtt_writer.py Download

from __future__ import print_function

# Import pynrfjprog API module
from pynrfjprog import LowLevel
from time import sleep

TEST_STRING = b'RTT Channel 1 write test #'


def run(snr=None):
    """
    Run example script.

    @param (optional) int snr: Specify serial number of DK to run example on.
    """
    print('# RTT read example using pynrfjprog started...')
    
    # Detect the device family of your device. Initialize an API object with UNKNOWN family and read the device's family. This step is performed so this example can be run in all devices without customer input.
    print('# Opening API with device family UNKNOWN, reading the device family.')
    with LowLevel.API(LowLevel.DeviceFamily.UNKNOWN) as api:            # Using with construction so there is no need to open or close the API class.
        if snr is not None:
            api.connect_to_emu_with_snr(snr)
        else:
            api.connect_to_emu_without_snr()
        device_family = api.read_device_family()
    
    # Initialize an API object with the target family. This will load nrfjprog.dll with the proper target family.
    api = LowLevel.API(device_family)
    
    # Open the loaded DLL and connect to an emulator probe. If several are connected a pop up will appear.
    api.open()
    try:

        if snr is not None:
            api.connect_to_emu_with_snr(snr)
        else:
            api.connect_to_emu_without_snr()

        # Erase all the flash of the device.
        print('Starting RTT.')
        api.rtt_start()
		
		# rtt_start() API is non-blocking, need to wait for the control block to be found
        while(api.rtt_is_control_block_found() != True): 
			print("waiting for control block")
			sleep(0.1)

        channel_count_down, channel_count_up = api.rtt_read_channel_count()
        print("Found {} down channels and {} up channels".format(channel_count_down, channel_count_up))
        cnt = 0
        while(True):
			api.rtt_write(1, TEST_STRING + str(cnt) + '\0')
			cnt = cnt + 1
			sleep(2);
        
        api.close()

        print('# Example done...')

    except LowLevel.APIError:
        api.close()
        raise
    
 
if __name__ == '__main__':
    run()

[Tim Adu]

Thanks Jørgen, and apologies for the late response. I've been sidetracked by other tasks. Now I finally have time for this.

I currently use SDK 15.2.0. What peripheral example did you start with? (I'd like to have as close to your setup as possible to avoid nasty surprises).

[Jørgen Holmefjord]

I started out with the UART peripheral example. However, I do not think that any part of that example is used in the project I uploaded, so it should not really matter.

[Tim Adu]

Looks like it's working. I just have one issue with  the python environment (I use python 3.x). Did you test the scripts with python 2.x?

[Jørgen Holmefjord]

Yes, I tested with Python 2.7.15. I see from the release notes that pynrfjprog should support Python 3.6 at least, but you may have to modify the example to use it with Python 3.x.

[Tim Adu]

Great! I igot it working with python 3.x. Need to tweak the script for my own tests, but the basic read and write from both ends works! I have enough to get me running. Thanks Jørgen!