Capturing RTT Logs in GitHub Actions

Capturing logs (e.g from {% c-line %}RTT{% c-line-end %}, {% c-line %}UART{% c-line-end %}, {% c-line %}BLE{% c-line-end %}, {% c-line %}MQTT{% c-line-end %}, etc) from an embedded device typically requires streaming the logs to a {% c-line %}stdout{% c-line-end %} that a test script can read from. When doing on-target testing (i.e. testing on actual hardware) in a GitHub Actions workflow, it can be a bit tricky to capture those logs. Fortunately, the Lager API makes grabbing device logs extremely easy.

Below is a snippet of python code for capturing {% c-line %}RTT{% c-line-end %} logs from a nRF52833 MCU.

{% c-block language="python" %}
import time
from lager import lager

timeout_sec = 42

dut = lager.DUT() # create DUT object

dut.disconnect() #disconnect SWD debugger from DUT
dut.connect() #connect SWD debugger to DUT

with lager.RTT() as rtt:
   dut.reset(halt=False)
   start_time = time.time()
   while time.time() - start_time < timeout_sec:
     line = rtt.read_line(timeout=1).decode().strip()
     print(line)
{% c-block-end %}

This will read the {% c-line %}RTT{% c-line-end %} logs and print them inside the GH Actions container this script is running in. You could also save the logs to a file, push the logs to a S3 bucket, etc.

Then in your {% c-line %}workflow.yaml{% c-line-end %} file you call:

{% c-block language="yaml" %}
- name: My Test
       run: |
         lager python test.py
{% c-block-end %}

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Now, whenever this workflow gets called, you can see the logs being output.

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