3 KiB
| title |
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| USB Logging |
import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem';
Overview
If you are developing ZMK on a device that does not have a built in UART for debugging and log/console output,
Zephyr can be configured to create a USB CDC ACM device and the direct all printk, console output, and log
messages to that device instead.
:::warning Battery Life Impact
Enabling logging increases the power usage of your keyboard, and can have a non-trivial impact to your time on battery. It is recommended to only enable logging when needed, and not leaving it on by default.
:::
Kconfig
The CONFIG_ZMK_USB_LOGGING Kconfig enables USB logging. This can be set at the keyboard level, typically in the config/<your_keyboard>.conf
file if you are using a user config repository. It can also be enabled at the ZMK level using the app/prj.conf file, or other
search locations described in the configuration overview.
Logging can be further configured using Kconfig described in the Zephyr documentation.
For instance, setting CONFIG_LOG_PROCESS_THREAD_STARTUP_DELAY_MS to a large value such as 8000 might help catch issues that happen near keyboard
boot, before you can connect to view the logs.
:::note
In Github Actions, you can check the <Keyboard> Kconfig file step output to verify the options above have been enabled
for you successfully.
:::
# Turn on logging, and set ZMK logging to debug output
CONFIG_ZMK_USB_LOGGING=y
Viewing Logs
After flashing the updated ZMK image, the board should expose a USB CDC ACM device that you can connect to and view the logs.
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On Linux, this should be a device like /dev/ttyACM0 and you can connect with minicom or tio as usual, e.g.:
sudo tio /dev/ttyACM0
On Windows, you can use PuTTY. Once installed, use Device Manager to figure out which COM port your controller is communicating on (listed under 'Ports (COM & LPT)') and specify that as the 'Serial line' in PuTTY.
If you already have the Ardunio IDE installed you can also use its built-in Serial Monitor.
On macOS, the device name is something like /dev/tty.usbmodemXXXXX where XXXXX is some numerical ID.
You can connect to the device with tio (can be installed via Homebrew):
sudo tio /dev/tty.usbmodem14401
You should see tio printing Disconnected or Connected when you disconnect or reconnect the USB cable.
From there, you should see the various log messages from ZMK and Zephyr, depending on which systems you have set to what log levels.