SDS011 dust sensor, checksum errors

[m_t]

Hi, has anyone here used the SDS011 dust sensor before? I'm using the USB-to-serial adapter that came with the sensor on a Raspberry Pi Model B Plus and I get occasional checksum errors. I'm wondering if those are really transmission errors or just a way for the sensor to indicate a measurement is invalid since all other values including the actual measurements are just fine:

PM 2.5: 2.200000, PM 10: 9.100000
header  : pass
cmd     : pass
checksum: fail
checksum: 0x0a, expected: 0x0d
tail    : pass

Here's my code https://github.com/m-thu/sandbox/blob/master/sds011/sds011.c and some shell scripts to generate plots: https://github.com/m-thu/sandbox/tree/master/sds011.