hidapi_co2mon.py

# do not forget to provide permisson to your device like:
# $ sudo chmod go+rw /dev/bus/usb/001/005
#
#
# or create udev rule in file /etc/udev/rules.d/50-local-raw-usb.rules:
# SUBSYSTEM=="usb", ATTRS{idVendor}=="04d9", ATTRS{idProduct}=="a052",  MODE="0666"
# 
# and restart udev 
# $ sudo udevadm control --reload-rules && sudo udevadm trigger
#
import hid
vid = 0x04d9
pid = 0xa052

try:
    print("Opening the device")

    h = hid.device()
    h.open(vid, pid) 

    print("Manufacturer: %s" % h.get_manufacturer_string())
    print("Product: %s" % h.get_product_string())
    print("Serial No: %s" % h.get_serial_number_string())

    print("Send feature report:")
    h.send_feature_report(bytearray([0xc4, 0xc6, 0xc0, 0x92, 0x40, 0x23, 0xdc, 0x96]))
    try:
        while True:
            r = h.read(8)
            if r:
                # print('read: "{}"'.format(r))
                metric = r[0]
                value = r[1]
                value_thousands = r[2]
                checksum = r[3]
                r4 = r[4]
                if r4 != 0x0d:
                    continue
                    print("Unexpected data from device")
                value_sum = metric + value + value_thousands

                metric_name = ""
                value_shifted = value << 8
                metric_value = value_shifted + value_thousands
                if metric == 0x42:
                    metric_name = "Temperature"
                    metric_value = metric_value / 16 - 273.15
                elif metric == 0x50:
                    metric_name = "CO2"
                elif metric == 0x44:
                    metric_name = "Humidity"
                else:
                    continue
                    metric_name = "Unknown"
                print(hex(metric), metric_name, "%.1f" % metric_value)


    finally:
        print("Closing the device")
        h.close()

    h.close()
except IOError as ex:
    print(ex)
    print("You probably don't have the hard-coded device.")
    print("Update the h.open() line in this script with the one")
    print("from the enumeration list output above and try again.")

print("Done")