STM32 · Embedded · 04
ECG, PPG, and APG Analog Front End
The sensor sheet separates the INA128 ECG input, OPA2333 filter/buffer stages, the SFH7070 PPG sensor, and the Vcm reference. I check analog gain and bias before interpreting ADC codes.
What I checked first
The sensor sheet separates the INA128 ECG input, OPA2333 filter/buffer stages, the SFH7070 PPG sensor, and the Vcm reference. I check analog gain and bias before interpreting ADC codes.
Source view
- ECG_LA and ECG_RA feed an instrumentation amplifier before the ECG output net.
- The PPG photodiode and green LEDs feed OPA2333 stages before the PPG output.
- The APG path carries changing PPG components through a separate stage.
Implementation path
Only the saved configuration and processing sequence are shown.
Key terms
- INA128
- OPA2333
- SFH7070
- Vcm
Review sequence
- INA128
- OPA2333 → SFH7070
- Vcm
Official references
- STM32CubeF4 Getting Started (UM1730)
- STM32 DSP with CMSIS (AN4841)
- Arm CMSIS-DSP
- STM32CubeF4 repository
The reviewed sources contain 22 prototype photos, a 40-slide STM setup deck, a three-page KiCad schematic, an ADC/UART note, an HRV module, two PPG code records, twelve top-level ECG C variants, and a complete CubeIDE project archive. I do not count byte-identical variants or ST/Arm vendor files as separate results, and I make no new performance claim without saved measurements.