RS41 adapter

rs41-rs

This repo contains a new approach to a firmware for the Vaisala RS41 radiosonde, written entirely in Rust.

:warning: 2024-05-03: Today I captured a RS41 with a new microcontroller: STM32L412. This repo is developed on the old revision (with STM32F100). Do not attempt to flash a new revision with this firmware! A new version might be on it's way some day.

Obtaining the sonde

The web contains lots of information about how to get and program a RS41. I am using a standard NXP LPC Link 2 with CMSIS-DAP firmware connected to the sonde with the adapter (see KiCad project in the hw folder). LPC-Link J2 must be closed.

Please unsolder and remove the antenna (steel wire next to the 10 pin connector) before first programming!

I have additionally mounted a SMA plug to connect to a SDR (LimeSDR) or analyzer, with a 10 dB pad between.

Sonde hardware

bazjo did an amazing job in reverse-engineering the RS41's PCB. Please read the documentation: https://github.com/bazjo/radiosonde_hardware/tree/master/Vaisala_RS41

Currently working features:

☑️ Flashing the sonde

☑️ RTIC running

☑️ LEDs indicating status:

• Blinking red LED indicates missing GPS lock
• Green LED indicates communication between STM32 and ublox

☑️ Power button and battery voltage (reading ADC)

☑️ Radio configuration:

• frequency
• tx power
• modulation
• GPIOs (heater)

☑️ Generating ubx messages

☑️ Sending ubx messages to u-blox GPS receiver and parsing responses

☑️ Transmitting data via (G)FSK and Hellschreiber mode

• Coordinates and height
• Callsign
• UTC
• GPS status

The (G)FSK mode also transmits

• sequence number
• CRC

You will find the (G)FSK receiver project here: https://codeberg.org/dl2ssb/rs41_rx-rs

Unlocking the flash:

I am running a stock Arch Linux. Other distros or even OSs have not been tested yet.

First terminal: open openocd

openocd -f interface/cmsis-dap.cfg -c "transport select swd"  -f target/stm32f1x.cfg

Second terminal: commands to openocd and unlock:

telnet 127.0.0.1 4444

> flash protect 0 0 15 off

For some sondes the command above did not work. You can try:

telnet 127.0.0.1 4444

> reset halt
> stm32f1x unlock 0

Building the firmware

$ git clone https://github.com/arnobert/rs41_rust
$ cd rs41_rust
$ cargo fetch
$ cargo build

With Hellschreiber mode:

$ cargo build --features "hell"

Flashing the sonde, GFSK/HELL:

$ cargo embed
$ cargo embed --features "hell"

Cargo embed auto-detects the LPC-Link. Other programmers might also work, but have not been tested.