ESP32 Modbus and RS485 data logger

Read the implementation

regToFloat / readFlowRate / readPositiveAccum · selected source lines 31–52. Source inspection is not a hardware test.

float regToFloat(uint16_t hi, uint16_t lo) {
  union { uint32_t U; float F; } u;
  u.U = ((uint32_t)hi << 16) | lo;
  return u.F;
}
// Read instantaneous flow (m³/h), then convert to L/s
float readFlowRate() {
  if (node.readHoldingRegisters(0x0000, 2) != node.ku8MBSuccess) return NAN;
  return regToFloat(node.getResponseBuffer(0), node.getResponseBuffer(1)) * 0.2778;  
}

// Read positive accumulator (LONG + fraction)
float readPositiveAccum() {
  // INTEGER part at reg 0009 -> offset 8, fraction at 0011 -> offset 10
  if (node.readHoldingRegisters(0x0008, 4) != node.ku8MBSuccess) return NAN;
  // lower two regs = integer, upper two = fraction
  int32_t N  = (int32_t)node.getResponseBuffer(0) << 16
             | node.getResponseBuffer(1);
  float   Nf = regToFloat(node.getResponseBuffer(2), node.getResponseBuffer(3));
  // multiplier n is handled in hardware (M33/M31), so assume direct (no extra 10ⁿ)
  return N + Nf;
}