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https://github.com/robert-hh/hx711

MicroPython driver for the HX711 load cell interface.
https://github.com/robert-hh/hx711

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MicroPython driver for the HX711 load cell interface.

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README 

        
# HX711: Python class for the HX711 load cell



This is a very short and simple class. This lib includes two variants of the

module. One is using direct GPIO pin handling, the other uses SPI. Besides

the class instantiation, both variants offer the same methods.



## Constructor



### hx711 = HX711(clock_pin, data_pin, gain=128)



This is the GPIO constructor. data_pin and clock_pin are the pin objects

of the GPIO pins used for the communication. clock_pin must not be an input-only pin.

gain is the setting of gain and channel of the load cell amplifier.

The default value of 128 also selects channel A.



### hx711 = HX711(clock_pin, data_pin, spi, gain=128)



This is the SPI constructor. data_pin is the SPI MISO, clock_pin the SPI MOSI. These must be

Pin objects, with data_pin defined for input, clock_pin defined as output. The must be supplied

in addition to the spi object, even if spi uses the same  pins for miso and mosi.

spi is the SPI object. The spi clock signal will not be be used.

gain is the setting of gain and channel of the load cell amplifier.

The default value of 128 also selects channel A.



### hx711 = HX711(clock_pin, data_pin, gain=128)



This is the Raspberry Pi PIO constructor. data_pin and clock_pin are the pin objects

of the GPIO pins used for the communication. clock_pin must not be an input-only pin.

gain is the setting of gain and channel of the load cell amplifier.

The default value of 128 also selects channel A.



## Methods



### hx711.set_gain(gain)



Sets the gain and channel configuration which is used for the next call of hx711.read()



|Gain|Channel|

|:-:|:-:|

|128|A|

|64|A|

|32|B|



### result = hx711.read()



Returns the actual raw value of the load cell. Raw means: not scaled, no offset

compensation.



### result = hx711.read_average(times=3)



Returns the raw value of the load cell as the average of times readings of The

raw value.



### result = hx711.read_lowpass()



Returns the actual value of the load cell fed through an one stage IIR lowpass

filter. The properties of the filter can be set with set_time_constant().



### rh = hx711.set_time_constant(value=None)



Set the time constant used by hx711.read_lowpass(). The range is 0-1.0. Smaller

values means longer times to settle and better smoothing.

If value is None, the actual value of the time constant is returned.



### value = hx711.get_value()



Returns the difference of the filtered load cell value and the offset, as set by hx711.set_offset() or hx711.tare()



### units = hx711.get_units()



Returns the value delivered by hx711.get_value() divided by the scale set by

hx711.set_scale().



### hx711.tare(times=15)



Determine the tare value of the load cell by averaging times raw readings.



### hx711.power_down()



Set the load cell to sleep mode.



### hx711.power_up()



Switch the load cell on again.



## Examples



```

# Example for Pycom device, gpio mode

# Connections:

# Pin # | HX711

# ------|-----------

# P9    | data_pin

# P10   | clock_pin

#



from hx711 import HX711

from machine import Pin



pin_OUT = Pin("P9", Pin.IN, pull=Pin.PULL_DOWN)

pin_SCK = Pin("P10", Pin.OUT)



hx711 = HX711(pin_SCK, pin_OUT)



hx711.tare()

value = hx711.read()

value = hx711.get_value()

```



```

# Example for micropython.org device, gpio mode

# Connections:

# Pin # | HX711

# ------|-----------

# 12    | data_pin

# 13    | clock_pin

#



from hx711 import HX711

from machine import Pin



pin_OUT = Pin(12, Pin.IN, pull=Pin.PULL_DOWN)

pin_SCK = Pin(13, Pin.OUT)



hx711 = HX711(pin_SCK, pin_OUT)



hx711.tare()

value = hx711.read()

value = hx711.get_value()

```



```

# Example for micropython.org device, RP2040 PIO mode

# Connections:

# Pin # | HX711

# ------|-----------

# 12    | data_pin

# 13    | clock_pin

#



from hx711_pio import HX711

from machine import Pin



pin_OUT = Pin(12, Pin.IN, pull=Pin.PULL_DOWN)

pin_SCK = Pin(13, Pin.OUT)



hx711 = HX711(pin_SCK, pin_OUT)



hx711.tare()

value = hx711.read()

value = hx711.get_value()

```



```

# Example for Pycom device, spi mode

# Connections:

# Pin # | HX711

# ------|-----------

# P9    | data_pin

# P10   | clock_pin

# None  | spi clock

#



from hx711_spi import HX711

from machine import Pin, SPI



pin_OUT = Pin("P9", Pin.IN, pull=Pin.PULL_DOWN)

pin_SCK = Pin("P10", Pin.OUT)



spi = SPI(0, mode=SPI.MASTER, baudrate=1000000, polarity=0,

             phase=0, pins=(None, pin_SCK, pin_OUT))



hx = HX711(pin_SCK, pin_OUT, spi)



hx711.tare()

value = hx711.read()

value = hx711.get_value()

```



```

# Example for micropython.org device, spi mode

# Connections:

# Pin # | HX711

# ------|-----------

# 12    | data_pin

# 13    | clock_pin

# 14    | spi clock



from hx711_spi import HX711

from machine import Pin



pin_OUT = Pin(12, Pin.IN, pull=Pin.PULL_DOWN)

pin_SCK = Pin(13, Pin.OUT)

spi_SCK = Pin(14)



spi = SPI(1, baudrate=1000000, polarity=0,

          phase=0, sck=spi_SCK, mosi=pin_SCK, miso=pin_OUT)



hx = HX711(pin_SCK, pin_OUT, spi)



hx711.tare()

value = hx711.read()

value = hx711.get_value()

```