Sparkfun Load Cell Amp Firmware

How to build tests

espidf

esp-idf must be installed and $IDF_PATH must be set (source ~/esp/esp-idf/exports.sh or similar) Then just run make espidftest

Datasheet

https://cdn.sparkfun.com/assets/b/f/5/a/e/hx711F_EN.pdf This is the Datasheet for the particular IC that is used on the Sparkfun Load-Cell Amp.

Interface Description

Details

• Supply Voltage: 2.6 - 5.5V

• XI = 0: On-Chip Oscillator

• RATE = 0: 10Hz Signal

• Data is signed 2's complement 24 bit (TO BE TESTED: Negative numbers?)

Serial interface:

• Clock Signal (IN)

  • Minimum frequency is 20 kHz (If 0.5 duty cycle is used)
  • Default frequency is 500 kHz
  • Maximum frequency is 2.5 MHz
  • PD_SCK can onset 0.1us after DOUT has fallen

• Data Signal (OUT)

  • When DOUT goes low, Data is available.
  • 25 or 27 pulses should be sent on PD_SCK, clocking the serial data out.
  • The data can be read 0.1us after the clock pulse arrived.

• Powering Down

  • Default PD_SCK = 0
  • if PD_SCK for > 60us: IC powers down
  • if IC powered down and PD_SCK -> 1: Power up again

Checklist:

• Connect Load-Cell to Amp, Connect Voltage source, Measure output with LA
• Write tests for LoadCellAmp class implementation
• Implement class LoadCellAmp
• Write tests for init function
• Implement constructor, destructor and init function
• Write tests for getReading function
• Implement getReading function
• Write tests for interrupts
• Implement interrupts
• Write a test application to demonstrate proper functionality

Testresults:

• The frequency at which new datapoints arrive is 11.85Hz rather than 10Hz. This may be due to the fact that we are using 3.3V instead of 5V