hi,
i’d like to use extra uart on ALL-H3-CC (H5). it’s not clear to me how to enable this. it looks like it is done with wiring tool described in Libre Computer Wiring Tool but it seems there’s no premade devicetree overlay and i did not understand how to make it myself from the documentation. i think some better docs on the development process for this would go a long way since it seems someone else asked recently about enabling uart on a different board.
Hi,
Writing Device Tree Overlays is a HUGE skill-set that likely you’re not going to learn from a forum post. I’m still learning this topic and it’s slow going, but when I feel up to it I’ll try to write a beginners guide. I’m certainly not there yet, and I wouldn’t hold your breath.
In the mean time I’ll do as @librecomputer does and suggest checking out the existing overlays:
For your board: libretech-wiring-tool/libre-computer/all-h3-cc-h5/dt at master · libre-computer-project/libretech-wiring-tool · GitHub
Here is the full Device tree for your board: https://boot.libre.computer/ci/all-h3-cc-h5.dts
For the ams-s905x-cc (which has more overlays written for it):libretech-wiring-tool/libre-computer/aml-s905x-cc/dt at master · libre-computer-project/libretech-wiring-tool · GitHub
Probably not relevant for a UART overlay, but I’ve found looking at overlays for other boards and trying to adapt them can be helpful, but steer clear of Raspberry Pi overlays (or take them with a grain of salt), as they’re full of fruity nonsense that is specific to the Broadcom SOCs they use.
I hope this helps.
If you (or anyone else) comes across good learning resources for this topic please share them! Us non-embedded engineers can use all the help we can get in this department.
Hey, super late reply. I shelved my project for a long time, but I’m just now picking it back up. i have the H5 board as well.
If you still need help making an overlay, i have some notes and may be able to help. I did this for a klipper screen for one of my 3d printers. I ended up just staying headless until i fixed the issue.
sudo apt update
sudo apt install git
git clone https://github.com/libretech-computer-project/libretech-wiring-tool.git
cd libretech-wiring-tool
sudo ./install
that should install the wiring tool
sudo ldto list
sudo ldto enable
sudo ldto merge
sudo ldto reset
sudo reboot
reboot for overlay to take effect, but some may work instantly.
I’m sure someone can explain this more thoroughly than I can. I don’t understand fully what I’m doing, but i can usually tinker around and get close.
The default UART, 3 pins on the board edge, is enabled by default. See Libre Computer Board Debug Serial UART Connection and Setup Guide