Raspberry Pi PicoW + LeRobot SO-ARM100 controlled via a webpage/mqtt/openai

Standalone Raspberry Pi Pico W / Pico 2 W controller for an SO-101 / SO-100 arm

Can control over WiFi via an internal Web Page, MQTT or openAI response API compatible remote\

Video: https://www.youtube.com/shorts/e_Y3U83MK2A

I had an RC car and a LeRobot SO-ARM100 and wanted to see if I can combine them and use an LLM to control...

The arm is drawn in 3D from what the servos report; click a dot to put a target down, Go (or Enter) sends the jaws there.

Calibration: set up limits for joints so arm doesn't self destruct... (don't ask)

3D mapping: tell robot which way is left or up

Poses: various poses described for openAI LLM knowledge base

AI: chat box with status responses. The microphone needs https

Drive: Virtual joystick to control the wheels, or you can connect a gamepad

How do I set it up

Items to do before

Picohive (optional) - for Debug logs and OTA updates

Add Device on picohive (generate the UUID, MQTT password and log key, pick a name)

Open the device, go to Device Config, press Export and copy the line for step 4 below

OpenAI (optional) - for AI chat box

An API key and a model (ex: gpt-6.1-sol) on a server that has responses API with storage

Flash a pico, it starts as access point picow_config / randompassword (...ultra secure password...)

Connect to the access point, the page opens by itself, if not, use http://192.168.4.1

Configure wifi and a user/pass for the web ui

Optional:

4.1. Remote server enter line from picohive for logging/OTA/crash reporting

4.2. OpenAI enter the URL, key, model and prompt

Reboot - joins your wifi, you can access via its new IP now (find it in picohive logs or on router)

Reconfigure any time from its new ip address

Tip

If you need to wipe, just use the universal flash_nuke.uf2 to wipe the flash then re-flash the firmware

Add servos one at a time to pico to set their IDs to not overlap (and baud rate to 115200, 1M was too much for my setup with 1K resistor)

Calibrate from web page (just press the calibrate and move the arm by hand so it learns limits)

Go to 3D model and map some positions so it knows left from right and up from down...

git clone --recursive https://github.com/AdrianCX/picohive-robotarm.git cd picohive-robotarm os/build_via_podman.sh pico2_w # or pico_w

Flash build/<board>/robotarm.uf2 Later updates for OTA need the encrypted file robotarm.uf2.encrypted Before you build your own, create your own OTA keys and certificate, as described in os/docs/ota.md. The HTTPS certificate is util/make_cert.sh <address>.

The same app builds on Linux with simulated servos

Useful to work on web page with valgrind and gdb

os/build_via_podman.sh linux # build/linux/robotarm os/run_via_podman.sh # http://localhost:8080, https://localhost:8443 os/run_via_podman.sh --valgrind # or --gdb

Memory usage

[2026-10-25 13:52:12] 192.168.100.69 657 app[build/pico_w/robotarm] version[1.0] os[b697060-dirty] buildid[db40f1ac39e2b3ee3d07d2199aa628118cf588b3] Heap[12308/223652] Free[211344] MinFree[151552] LargestFree[192458] Stack[4236/16384] lastRestartReason[reboot_command]

There's quite a lot of free memory on pico even in worst case (150KB), stack usage is reasonable

Wiring (defaults in src/config/general_config.h, change them there if you wire it differently):

The bus is half duplex - one data wire shared by every servo. The pico's pins are 3.3V: check a servo's data wire idles at or below that, or put a level shifter in between. The Waveshare bus servo driver board does all of this already, and plugs into the same two pins.

Two pins of one motor share a PWM slice (gpio/2 % 8, even A, odd B), keep that if you move them. MOTOR_PWM 1 drives the pins as PWM, 0 is on/off.

The diagram is generated: python3 docs/pictures/wiring.py docs/pictures/wiring.svg

AGPL-3.0-or-later for this app. The os/ submodule is MPL-2.0, see its LICENSE.