OSError: [Errno 90] EMSGSIZE

[Zino Henderickx]

Hi everyone, I am working on a project.
When I send a bytestring to LoRa I get a error because my bytestring is to long.

Does someone know how I can resolve this problem?

import pycom
import machine
import time
from machine import Pin
import socket
from network import LoRa
import binascii
import array
from machine import PWM




############### LoRa Connectie ###############
lora = LoRa(mode=LoRa.LORAWAN, region=LoRa.EU868)

app_eui = binascii.unhexlify('70B3D57ED003B935')
app_key = binascii.unhexlify('D0258B34705B17B2DD2C87CA07CA5D68')

lora.join(activation=LoRa.OTAA, auth=(app_eui, app_key), timeout=0)

# wait until the module has joined the network
while not lora.has_joined():
    time.sleep(2.5)
    print('Not joined yet...')

print('Network joined!')

############### Weightsensor ###############
def main():
    while True:
        adc = machine.ADC()             # create an ADC object
        apin = adc.channel(pin='P16')   # create an analog pin on P16
        val = apin()
        low = apin()                    # read an analog value
        high = apin()                    # read an analog value

        if val < 20:
            print(val)
            print("Weight is good")
            binaryString = bin(low)
            print(binaryString)
            time.sleep(2.5)
        if val > 20:
            print(val)
            print("Weight is to high")
            binaryString = bin(high)
            print(binaryString)
            time.sleep(2.5)
            # 50% duty cycle at 38kHz.
            pwm = PWM(3, frequency=78000)  # use PWM timer 0, with a frequency of 5KHz
            # create pwm channel on pin P12 with a duty cycle of 50%
            pwm_c = pwm.channel(0, pin='P20', duty_cycle=1.0)
            pwm_c.duty_cycle(0.3) # change the duty cycle to 30%


        s = socket.socket(socket.AF_LORA, socket.SOCK_RAW)
        s.setsockopt(socket.SOL_LORA, socket.SO_DR, 5)
        s.setblocking(False)
        s.send(bytes(high))



if __name__ == "__main__":
    main()

[robert-hh]

@Zino-Henderickx The pyaload size of a Lora message depends on the spreading factor, and ranges e.g. for EU868 between 51 and 222 bytes, for US915 between 11 and 222 bytes . How long is the byte strings you attempt to send, and which spreading factor are you using?

[jcaron]

@Zino-Henderickx you should probably use ustruct to pack your value rather than bytes directly on a float. Don’t have a device at hand to test, but I suspect the latter sends a text version of the float, which can be quite long.

It shouldn’t be a problem at DR5 though. Log the size and contents of your payload, it should be informative.

[robert-hh]

@Zino-Henderickx Just spotted the reason:

the line:
s.send(bytes(high))
sends bytes(high), which is a bytearray with the number of bytes, which is given by the value of high. So if high is 1000, it will create a 1000 bytes long object.
You may use str(high).endcode(), or use struct.pack() as @jcaron mentioned.

[Zino Henderickx]

@jcaron Yes I will try that. Thanks for the advice!