markjb/python-pms7003

Python script to test a Plantower PMS7003 serial laser particulate sensor

python-pms7003's Issues

Error while execution

Hi,
When i print data it gives
data= b'\x00\x1c\x00,\x00I\x00M\x00\x1f\x002\x00> \x1c\t:\x01\xca\x00&\x00\x06\x00\x02\x97\x00\x04\x0b'

frameLength = ord(data[1]) + (ord(data[0])<<8)

the above line gives this error
TypeError: ord() expected a character, but string of length 2 found

Regarding wrong calculation.

Hi Mark,
In the meantime, it looks like your checksum calculation is wrong:

        # Calculate the payload checksum (not including the payload checksum bytes)
        inputChecksum = 0x42 + 0x4d
        for x in range(0, 27):
            inputChecksum = inputChecksum + data[x]

Here, range(0, 27) will only give you the first 27 indexes ([0, 1, ..., 26]).
You need the first 28 indexes, as the last
2 are the checksum.
Instead you can write the checksum calculation as:

        # Calculate the payload checksum (not including the payload checksum bytes)
        inputChecksum = 0x42 + 0x4d + sum(data[:-2])

Please let me know if i am wrong.
Thank you.

Units of Readings

Hi Mark,
I am getting this type of readings.

Date_Time | PM1 | PM2.5 | PM10
2019/02/14 09:52:35 | 260 | 2854 | 3936

Can you tell me what can be the unit of this readings?

Thank you.