I'm just playing with a load cell for an upcoming project and struggling with an odd sample rate behavior.
The board is a Mega2650.
I'm using the HX711_ADC library and have the hardware configured for 80Hz. The first 6 samples are returned at 80Hz (~12ms) and then there is one sample at ~50Hz and the rest are dead even at 40Hz indefinitely. Can't find any timers in the library or code, could this be a hardware issue? Cheap amazon HX711's.
Code copied below is straight out of the library example except for printing some .csv values to log.
Thanks,
Alex
#include <HX711_ADC.h>
#include <EEPROM.h>
//pins:
const int HX711_dout = 4; //mcu > HX711 dout pin
const int HX711_sck = 5; //mcu > HX711 sck pin
//HX711 constructor:
HX711_ADC LoadCell(HX711_dout, HX711_sck);
const int calVal_eepromAdress = 0;
long t;
void setup() {
Serial.begin(9600); delay(2);
//Serial.println();
//Serial.println("Starting...");
LoadCell.begin();
float calibrationValue; // calibration value (see example file "Calibration.ino")
//calibrationValue = 3480.0; // uncomment this if you want to set the calibration value in the sketch
#if defined(ESP8266)|| defined(ESP32)
//EEPROM.begin(512); // uncomment this if you use ESP8266/ESP32 and want to fetch the calibration value from eeprom
#endif
EEPROM.get(calVal_eepromAdress, calibrationValue); // uncomment this if you want to fetch the calibration value from eeprom
long stabilizingtime = 2000; // preciscion right after power-up can be improved by adding a few seconds of stabilizing time
boolean _tare = true; //set this to false if you don't want tare to be performed in the next step
LoadCell.start(stabilizingtime, _tare);
if (LoadCell.getTareTimeoutFlag()) {
Serial.println("Timeout, check MCU>HX711 wiring and pin designations");
while (1);
}
else {
LoadCell.setCalFactor(calibrationValue); // set calibration value (float)
//Serial.println("Startup is complete");
}
}
void loop() {
static boolean newDataReady = 0;
const int serialPrintInterval = 0; //increase value to slow down serial print activity
// check for new data/start next conversion:
if (LoadCell.update()) newDataReady = true;
// get smoothed value from the dataset:
if (newDataReady) {
if (millis() > t + serialPrintInterval) {
float i = LoadCell.getData();
float j = LoadCell.getSPS();
t = millis();
Serial.print("DATA,");
Serial.print(t);
Serial.print(",");
Serial.print(i);
Serial.print(",");
Serial.print(j);
Serial.println(",");
newDataReady = 0;
//t = millis();
}
}
// receive command from serial terminal, send 't' to initiate tare operation:
if (Serial.available() > 0) {
float i;
char inByte = Serial.read();
if (inByte == 't') LoadCell.tareNoDelay();
}
// check if last tare operation is complete:
if (LoadCell.getTareStatus() == true) {
//Serial.println("Tare complete");
}
}