QR-Code Reader - Trigger read from serial port and read code value

qrcoder

Re: ATOMIC QR-CODE READER - Documentation - Trigger in Host Mode

Seems obvious that it should be possible to trigger the reading of a QR code from the serial port and read the code value after that. I have tried but failed. Reading the value works fine fut so far only the button trigger mode works reliably.

Has someone made this work that could share what settings are necessary and how the trigger is sent through the serial port?

Best regards

Cognitive5525

Have you read this document?

qrcoder

Yes, I have seen that document, but it is not clear to me what sequence of commands is necessary to trigger the reading of a QR code from the serial port.
Is the sequence something like:

Send wake-up and wait 50ms ( 0x0)
Send host command (0x 07 C6 04 08 00 8A 08 FE 9)
what now?
start decoding (0x 04 E4 04 00 FF 14) wait x ms
stop decoding (0x 04 E5 04 00 FF 13)
read from serial port

or is the sequence something else?

Grateful for your help!

Cognitive5525

From this Arduino example the answer is yes.

Note I think there is a typo in line 49.

Serial2.write(start_scan_cmd, sizeof(stop_scan_cmd));

should probably be

Serial2.write(stop_scan_cmd, sizeof(stop_scan_cmd));

qrcoder

I think I still am doing something wrong. In the example below it seems that the M5 isn't reacting to the commands. Do I have to scan a QR code from the manual first to get it into the proper state?

Example 1:

import serial
import time

wakeup_cmd = bytes([0x00])
host_mode_cmd = bytes([0x07, 0xC6, 0x04, 0x08, 0x00, 0x8A, 0x08, 0xFE, 0x95])
start_scan_cmd = bytes([0x04, 0xE4, 0x04, 0x00, 0xFF, 0x14])
stop_scan_cmd = bytes([0x04, 0xE5, 0x04, 0x00, 0xFF, 0x13])

print('Open serial port')
ser = serial.Serial('COM4', 9600, timeout=1)  # Adjust the port name and baud rate as needed

try:
    print('Wake up!')
    ser.write(wakeup_cmd)
    time.sleep(0.05)
    
    print('Host mode')
    ser.write(host_mode_cmd) 
    time.sleep(0.5)
    
    print('Start scan')
    ser.write(start_scan_cmd)
    time.sleep(3)

    print('Stop scan')
    ser.write(stop_scan_cmd)
    time.sleep(1)

    print('Bytes waiting at serial port: ' + str(ser.in_waiting))
    response = ser.read(ser.in_waiting)
    print("Received:", response.decode())

except Exception as e:
    print("Error communicating with serial device: ", e)

finally:
    print("Close serial port")
    ser.close()

The output:

Open serial port
Wake up!
Host mode
Start scan
Stop scan
Bytes waiting at serial port: 0
Received:
Close serial port

Doing something simpler doesn't work either:

Example 2:

software_version_cmd = bytes([0x04, 0xA3, 0x04, 0x00, 0xFF, 0x55])

print('Open serial port')
ser = serial.Serial('COM4', 9600, timeout=1)  # Adjust the port name and baud rate as needed

try:
    print('Wake up!')
    ser.write(wakeup_cmd)
    time.sleep(0.05)
    
    print('Check software version')
    ser.write(software_version_cmd)
    time.sleep(1)

    print('Bytes waiting at serial port: ' + str(ser.in_waiting))
    response = ser.read(ser.in_waiting)
    print("Received:", response.decode())

except Exception as e:
    print("Error communicating with serial device: ", e)

finally:
    print("Close serial port")
    ser.close()

The output:

Open serial port
Wake up!
Check software version
Bytes waiting at serial port: 0
Received:
Close serial port