v0.2.1 — automated dose metering

Sender firmware: READ REF now drives the head (same path as MEAS BLK/LIT), 3 s LED warm-up, 20-sample trimmed mean. RP2040 bridge is unchanged from 0.2.0.

1. ESP32-S3 (CH340 port, usually /dev/ttyUSB0):

sudo apt install esptool
esptool --chip esp32s3 --port /dev/ttyUSB0 --baud 921600 write_flash 0x0 \
  splitgrade-sensecap-sender-0.2.1.bin

2. RP2040 (optional, for TSL2591/AS7343): hold the internal BOOT button, plug the RP2040 USB-C, copy the .uf2 onto the RPI-RP2 disk.

Full steps: FLASH.md

Flash the LED head separately: https://github.com/Draganito/darkroom-enlarger-head/releases