Missing HX711 code in ESP32 - Here it is in lua script

[shetyespratham]

Missing feature

HX711 feature is missing in nodemcu of esp32. I have written and tested the code in Lua script which people can use.

Justification

HX711 is used by many and available with ESP8266. Having it in ESP32 will make people's life easier.

Workarounds

Lua Script I tested successfully on 40KG loadcell.

function tare(t)
sum=hx711_read()
sum=0
for i=1,t,1 do
sum=sum+hx711_read()
end
offsetAod=sum/t
isTare=1
return offsetAod
end
function getAverageWeight(t)
nowAodValue=0
for i=1,t,1 do
nowAodValue=nowAodValue+hx711_read()
end
nowAodValue=nowAodValue/t
print("newAodValue="..nowAodValue)
weight=(nowAodValue-offsetAod) * coefficient
return weight / -2.55 -- this is a calibration value (weight / actual weight)
-- when i checked known weight with the weight i was recieving here
-- you can remove this division and then check the weight of object for which you know the real weight
-- and then weight returned here / actual weight = calibration factor, which is -2.55 in my case
end
function hx711_read()
tmr.wdclr()
gpio.write(hx711_dat, 1)
gpio.config({gpio=hx711_dat, dir=gpio.IN })
count=1
ctr=1
gpio.write(hx711_clk, 0)

while(count == 1)
do -- waiting for hx711_dat to go LOW
count = gpio.read(hx711_dat)
ctr=ctr+1
end
tmr.wdclr()
count = 0
for i=0, 23 do -- receive 24 bits data
gpio.write(hx711_clk, 1)
gpio.write(hx711_clk, 0)
-- bit.lshift(count, 1)
count = count * 2 -- shift left by 1 bit
ctr=0
ctr=gpio.read(hx711_dat)
if ctr==1 then
count=count+1 -- set first bit ON if gpio hx711_dat is high
end
end
if count > 8388607 then -- when count > 8388607 i.e. 24th bit is ON so it is a simple version of XOR with x800000
count = count - 8388608
end
gpio.write(hx711_clk, 1)
gpio.write(hx711_clk, 0)
gpio.write(hx711_clk, 1)
gpio.write(hx711_clk, 0)
gpio.write(hx711_clk, 1)
gpio.write(hx711_clk, 0)
return count
end
hx711_clk=22
hx711_dat=23
count=0
isTare=0
offsetAod=0
weight=0
coefficient=-0.00004906289863605140
gpio.config( {gpio=hx711_clk, dir=gpio.OUT, pull=gpio.FLOATING}, {gpio=hx711_dat,
dir=gpio.IN_OUT, pull=gpio.FLOATING })
gpio.write(hx711_clk, 1)
print("tare value "..tare(10))
print("weight "..getAverageWeight(10))
-- END of the program --