Currently I’m working on a project where I want to use multiple scales in a fridge. When something will be taking out of the fridge the scale detects the different weight and send an event to my server. At this moment I can’t figure out why it’s not working…
I’m using a Raspberry Pi 4 Modal B with a pHat attached to the GPIO pins. Then the I2C signal goes to the first TCA9548A to use the bus with 8 different channels. After the first TCA9548A I have connected 3 more TCA9548A (with different addresses) for using multiple NAU7802 in my project. See image below.
(I need the 8 channels multiplexer because the I2C address of the NAU7802 is 0x2A and is hardware defined. A multiplexer/Mux is required to communicate to multiple NAU7802 sensors on a single bus.)
Now the problem that I’m facing is that the TCA9548A is working for the first two multiplexer. When the signal will go through the third multiplexer it can only find 1 NAU7802 sensor. (I have 3 connected to that mux). And the fourth multiplexer can only find 2 NAU7802 sensors. (I have 4 connected to that mux).
Now the strange thing is that when I connect only the first 3 muliplexers everything is working correctly. Why is the fourth multiplexer giving me this problem?
Products that I use:
SparkFun Qwiic pHAT v2.0 for Raspberry Pi
SparkFun Qwiic Mux Breakout - 8 Channel (TCA9548A)
SparkFun Qwiic Scale - NAU7802
Code:
import qwiic_tca9548a
import PyNAU7802
import smbus2
import time
import json
import requests
def enable_port(mux: qwiic_tca9548a.QwiicTCA9548A, port):
mux.enable_channels(port)
def disable_port(mux: qwiic_tca9548a.QwiicTCA9548A, port):
mux.disable_channels(port)
def initialize_mux(address):
mux = qwiic_tca9548a.QwiicTCA9548A(address=address)
return mux
def create_instance():
mux = []
addresses = [*range(0x70, 0x77 + 1)]
for address in addresses:
instance = initialize_mux(address)
if not instance.is_connected():
continue
print("Connected to mux {0} \n".format(address))
instance.disable_all()
mux.append({
"instance": instance,
"scales": [],
})
return mux
def create_bus():
bus = smbus2.SMBus(1)
return bus
def initialize_scales(mux):
scales = []
bus = create_bus()
ports = [0, 1, 2, 3, 4, 5, 6, 7]
for port in ports:
enable_port(mux, port)
nau = PyNAU7802.NAU7802()
if not nau.begin(bus):
# print(f"NOT CONNECTED TO SCALE: {port} \n")
disable_port(mux, port)
continue
print(f"Connected to port: {port} with mux: {mux.address} \n")
scales.append({
"port": port,
"nau": nau
})
disable_port(mux, port)
print(f"scales initialised: {scales} with mux: {mux.address} \n")
return scales
def get_calibration_data_file_name(mux):
return "tare_mux_" + str(mux["instance"].address) + ".json"
def main():
mux = create_instance()
for i, val in enumerate(mux):
mux[i]["scales"] = initialize_scales(mux[i]["instance"])
if __name__ == "__main__":
main()
Terminal:
pi@raspberrypi:~ $ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: 70 71 72 73 -- -- -- --
pi@raspberrypi:~ $ python3 test_connecting_scales.py
Connected to mux 112
Connected to mux 113
Connected to mux 114
Connected to mux 115
Connected to port: 0 with mux: 112
Connected to port: 3 with mux: 112
Connected to port: 4 with mux: 112
Connected to port: 7 with mux: 112
scales initialised: [{'port': 0, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a11d0>}, {'port': 3, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1210>}, {'port': 4, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1930>}, {'port': 7, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1630>}] with mux: 112
Connected to port: 0 with mux: 113
Connected to port: 3 with mux: 113
Connected to port: 4 with mux: 113
Connected to port: 7 with mux: 113
scales initialised: [{'port': 0, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1b30>}, {'port': 3, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1b50>}, {'port': 4, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1a90>}, {'port': 7, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb59a1a70>}] with mux: 113
Connected to port: 4 with mux: 114
scales initialised: [{'port': 4, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb5a30ad0>}] with mux: 114
Connected to port: 0 with mux: 115
Connected to port: 3 with mux: 115
scales initialised: [{'port': 0, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb5a309f0>}, {'port': 3, 'nau': <PyNAU7802.NAU7802.NAU7802 object at 0xb5a30a50>}] with mux: 115
Connection:
https://i.stack.imgur.com/wAoty.jpg
