IR receive data missing last two values of send data

[bradanlane]

I have written a simple IR test based on the CPE tutorial. It sends a list of 4 values and processes received data.

I am using the RPi PICOS with the Adafruit LED Emitter and 38kHz Receiver.

I am observing two problems.

1. the receive data is missing two values at the end. They represent the first value of a bit followed by the trail value. In my example, this is 600 and 0.
2. the received data is the 1s compliment of the send data. i.e. sending 255 receives 0; sending 251, receives 4.

Note: the 1s complement issue is an error in the CPX learning guide. A separate issue has been opened for the guide. The code below has been updated to the correct format.

Workaoround for missing values: Set the trail value to something (eg 100 or 255). Now the receiving end gets a full message plus a bad pulse. Test the pulse count and skip processing if it is too small. Sample code below has been updated.

Here is the code:

import board
import time
import random
import pulseio
import adafruit_irremote

IR_HEADER = [9000, 4000]
IR_START = 600
IR_SHORT = 600
IR_LONG = 1600
IR_ZERO = [IR_START, IR_SHORT]
IR_ONE  = [IR_START, IR_LONG]

ir_rx = pulseio.PulseIn(board.GP1, maxlen=200, idle_state=True)
ir_tx = pulseio.PulseOut(board.GP0, frequency=38000, duty_cycle=2**15)

decoder = adafruit_irremote.GenericDecode()
encoder = adafruit_irremote.GenericTransmit(header=IR_HEADER, one=IR_ONE, zero=IR_ZERO, trail=255, debug=True)

def ir_received(ir):
    pulses = decoder.read_pulses(ir)
    count = len(pulses)
    if count < 4:
        return
    # KLUDGE to append missing data
    #pulses.append(600)
    #pulses.append(0)
    print("Received: ", pulses)
    try:
        code = decoder.decode_bits(pulses)
        print("Received:", code)
    except Exception as e:
        print("Failed to decode:", e)

def ir_transmit(ir, value):
    if type(value) is not list:
        value = [value]
    print("sending: ", value)
    encoder.transmit(ir, value)

timer = time.time() + random.randint(5, 15)
message = [255, 253, 251, 249]

while True:
    if timer < time.time():
        timer = time.time() + random.randint(5, 15)
        ir_rx.pause()
        ir_transmit(ir_tx, message)
        ir_rx.resume()
    if len(ir_rx) > 0:
        ir_received(ir_rx)
    time.sleep(0.05)

[tkomde]

@bradanlane
I sent a PR two weeks ago ( #68 ) that addresses this issue. The samples in this repository should be fine, but I think the CPX learning guide is still intact. Sorry, but I don't know how to request a fix.

[bradanlane]

My apologies for not checking the PRs. Thank you for adding it to this issue.

As to the CPX documentation, I have already submitted an issue to that repository with the requisite correction.