Further check possible when reading values; avoids bad data about sps30

[paulvha]

hi,
Thanks for your feedback.
The issue is NOT SPS30 nor CRC failing. It works in many places without any problems for a long time. The problem is related to SoftSerial and the connection speed. SoftSerial is highly dependent on-time interrupt handling. As soon as the RX line detects a rising edge, which is an indication of a start, it will raise an interrupt. If that interrupt is not handled on-time, e.g the processor is busy already handling another interrupt, incoming bits will be missed from incoming characters on the RX line. Next to that, I have only seen SoftSerial work stable up to 56K (on a Mega2560). The SPS30 only works on 115K. Of course, you can as you did, increase checks to remove packets in error, but that getting a good packet is still "hope and pray". Especially if the processor load is increased e.g. by adding a WIFI connection. As I want a stable solution and therefore on an ESP8266 I only use I2C.

regards,
Paul