Platforms & Build

The firmware is built with PlatformIO using the Arduino framework. A single platformio.ini defines multiple environments — one per MCU family — so you can target any supported board without touching the source.

Quick Start

Install PlatformIO Core or the VS Code extension.

Clone the firmware repository:

git clone https://github.com/rpi-seism/reader.git
cd reader

Select your target environment and build:

# STM32 (recommended)
pio run -e stm32 -t upload

# RP2040
pio run -e rp2040 -t upload

# ESP32
pio run -e esp32 -t upload

`platformio.ini` Environments

[env:stm32]
platform  = ststm32
framework = arduino
board     = genericSTM32F103C8   ; Blue Pill — swap for your target
build_flags =
    -D PLATFORM_STM32
    -D SERIAL_RX_BUFFER_SIZE=512
lib_deps =
    robtillaart/CRC@^1.0.0

Notes:

HAL_NVIC_SystemReset() is available on all STM32 families.
Hardware UART1 is used for RS-422; USB virtual COM is available for debug.
The MAX490E DE/RE pins must be toggled around each transmission burst.

[env:rp2040]
platform  = raspberrypi
framework = arduino
board     = pico
build_flags =
    -D PLATFORM_RP2040
lib_deps =
    robtillaart/CRC@^1.0.0

Notes:

Programmable I/O (PIO) gives jitter-free SPI timing, ideal for the ADS1256.
Use Serial1 for RS-422; Serial (USB) for debug.
Reset is via watchdog_reboot(0, 0, 0) or rp2040.reboot().

[env:esp32]
platform  = espressif32
framework = arduino
board     = esp32dev
build_flags =
    -D PLATFORM_ESP32
lib_deps =
    robtillaart/CRC@^1.0.0

Notes:

Use HardwareSerial Serial2(2) for RS-422.
Wi-Fi interference can add jitter to SPI — disable Wi-Fi if not needed.
ESP.restart() is the reset function.
OTA updates are possible via the Arduino OTA library.

[env:avr_uno]
platform  = atmelavr
framework = arduino
board     = uno
lib_deps =
    robtillaart/CRC@^1.0.0

Notes:

Only 2 KB of SRAM — keep buffers minimal.
Software Serial is required for RS-422 (hardware UART is used by USB).
Recommended for prototyping only; timing jitter is higher than 32-bit targets.
No hardware reset API; use the watchdog timer (wdt.h).

[env:teensy40]
platform  = teensy
framework = arduino
board     = teensy40
lib_deps =
    robtillaart/CRC@^1.0.0

Notes:

600 MHz ARM Cortex-M7 — handles >500 SPS without issue.
Hardware SPI runs up to 40 MHz; use 4 MHz or lower for the ADS1256.
Multiple hardware UARTs available; use Serial1 or Serial2 for RS-422.

CRC-32 Library

The firmware uses robtillaart/CRC to compute the Ethernet/PKZip polynomial CRC-32, matching the daemon’s binascii.crc32():

#include "CRC32.h"

CRC32 crc;
crc.reset();
crc.add(packet_buffer, 14);   // header + 3 × int32
uint32_t checksum = crc.calc();
memcpy(&packet_buffer[14], &checksum, 4);

Dead-Client Detection

If the RS-422 link goes down (daemon crash, cable fault), the UART TX FIFO eventually overflows. The firmware tracks consecutive TX failures. After a configurable threshold it calls the platform reset function to reinitialise the UART hardware:

// Platform-specific reset
#if defined(PLATFORM_STM32)
  HAL_NVIC_SystemReset();
#elif defined(PLATFORM_ESP32)
  ESP.restart();
#elif defined(PLATFORM_RP2040)
  rp2040.reboot();
#else
  wdt_enable(WDTO_15MS);  // AVR watchdog
  while(1) {}
#endif

The daemon detects the MCU’s absence through its own RX timeout and in_waiting heartbeat monitor — both sides recover independently.

SPI Wiring (ADS1256)

ADS1256 Pin	MCU Pin	Signal
SCLK	SPI CLK	SPI Clock (1–4 MHz)
DIN	SPI MOSI	Data to ADC
DOUT	SPI MISO	Data from ADC
CS	GPIO (active low)	Chip Select
DRDY	GPIO (interrupt)	Data Ready (falling edge)
PDWN	3.3 V	Always powered
RESET	GPIO or VCC	Pull high for normal operation

Platforms & Build

Quick Start

platformio.ini Environments

CRC-32 Library

Dead-Client Detection

SPI Wiring (ADS1256)

`platformio.ini` Environments