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BIO-RAD PSU Controller

This project was built off the PicoEMP codebase.

Firmware for a Raspberry Pi Pico that controls a BIO-RAD 3000Xi high-voltage power supply. The Pico replaces the original front-panel controller, providing voltage regulation via a calibration table, a parabolic DAC ramp, and a USB serial command interface.

Hardware schematics are in the hardware/ folder. All active firmware is in firmware/c/.

Building the Firmware

Requires the Pico SDK.

export PICO_SDK_PATH=/path/to/pico-sdk
cd firmware/c
cmake -S . -B build
cmake --build build

Output: firmware/c/build/biorad.uf2

Flashing

Hold BOOTSEL on the Pico while connecting USB, then copy the .uf2 to the mounted RPI-RP2 drive. The Pico reboots automatically into the new firmware. To reflash, use the b command to reboot into bootloader mode.

Serial Console

Connect at any baud rate over USB-CDC. Type h for help. An empty line repeats the last command.

BIO-RAD Commands:

  System:
    h / help                show this help
    s / status              show all state at a glance
    r / reset               reset device
    b / bootload            reboot into USB firmware loading mode

  HV Output:
    hve                     hv_enable: enable HV output
    hvd                     hv_disable: disable HV output
    sv [V]                  set target voltage (capped at soft limit)
    lim                     set soft limit (sv cap) and hard limit (control ceiling)

  Monitoring:
    rv [period|freq|value]  read_voltage: all fields, or one (NULL if no signal/cal)
    ri [period|freq|value]  read_current: all fields, or one (value always NULL)

  DAC / Ramp:
    dacw [code]             dac_write: raw 12-bit code (0-4095); pauses ramp if HV on
    dacr                    dac_read: current DAC code
    sr                      set_ramp: parabolic ramp params (step_max, step_min, tick_ms)

  Calibration:
    cap [V]                 cal_capture: record cal point at measured volts
    cls                     cal_list: show voltage->DAC table
    crm                     cal_remove: remove a cal point by index
    csv                     cal_save: persist cal, limits, and ramp to flash
    crd                     cal_default: reset to compiled defaults (csv to persist)

  Faults:
    gf                      get_faults: show active fault flags
    cf                      clear_faults: clear sticky fault register
    fi [true|false]         fault_ignore: get state, or set on/off

Calibration workflow

  1. Enable HV output (hve) and set a DAC value (dacw 100).
  2. Measure the actual output voltage with a meter.
  3. Capture a cal point at the measured voltage (cap <measured_V>).
  4. Repeat across the desired voltage range.
  5. Save to flash (csv).

The control loop interpolates between captured points to map DAC codes to volts. cls shows the current table; crm removes a point by index; crd resets to compiled defaults.

Sample table:

Cal points (8):
  Idx | Voltage    | DAC    | PWM Frequency
  ----+------------+--------+--------------
    0 |    20.00 V |     48 |     242.97 Hz
    1 |    61.80 V |    100 |     765.91 Hz
    2 |   141.50 V |    200 |    1760.97 Hz
    3 |   221.60 V |    300 |    2758.77 Hz
    4 |   301.50 V |    400 |    3755.18 Hz
    5 |   381.40 V |    500 |    4752.15 Hz
    6 |   461.20 V |    600 |    5933.31 Hz
    7 |   541.25 V |    700 |    6747.82 Hz