Technical overview, architecture, and connector references for the Open-Source Leg Data Acquisition board.
The Data Acquisition Board enables high quality analog signal measurements for using the 6-channel load cell or other relevant analog signals. This is a separate circuit board that can be used with the RPi or other embedded systems via SPI communication. The Data Acquisition System (DAQ) integrates a 24-bit, 6-channel delta-sigma ADC (Texas Instruments ADS131M06) with external signal amplification and an anti-aliasing filter. A charge pump generates bipolar supply voltages from a single input to power bridge-based sensors. The DAQ is optimized for load cell measurements (SRI M3564F) for the Open-Source Leg and can also be used for high-resolution voltage measurements with bridge-based sensors.
Front view of the DAQ board.
ADC, timing, gain, and power specifications at a glance.
Core ADC and analog front-end specifications.
| Field | Value |
|---|---|
| Architecture | Delta-Sigma |
| Interface | SPI |
| Channels | 6 |
| Anti-aliasing cutoff (-3 dB) | 8 kHz |
| Gain Stage 1 (fixed) | Channels 1-3: 34, Channels 4-6: 151 |
| Gain Stage 2 (programmable) | 1-128 |
| Resolution | 24 bits |
| Sampling rate | 250 Hz-32 kHz |
| Operating voltage | 2.7 V-3.6 V |
| Bipolar output | +/-2.5 V |
| Max output current | 250 mA |
Mechanical envelope and connector definitions.
Board dimensions, mounting hole size, and connector interfaces.
| Field | Value |
|---|---|
| Length | 42 mm |
| Width | 26 mm |
| Mounting hole | 2.5 mm |
| SPI connector | Molex Pico-Clasp, 6-pin |
| Loadcell connector | Molex Pico-Blade, 14-pin |
SPI and loadcell connector pin definitions.
Pin-level connector mapping is documented in the DAQ datasheet.
