First measurement read in sps30_example_usage.c always fails

[rwaldura]

sps30_example_usage.c consistently fails to read the very first measurement, in my experience.

sps30-uart/sps30.h says:

sps30_start_measurement() - start measuring
Once the measurement is started, measurements are retrievable once per second
with sps30_read_measurement.

But sps30_example_usage.c calls sps30_start_measurement() right after sps30_start_measurement() -- the first time, without waiting one second before the call.

I propose moving the sleep call at
https://github.com/Sensirion/embedded-uart-sps/blob/master/sps30-uart/sps30_example_usage.c#L121
to line 95 instead, at the start of the loop.

With this change, all my measurements are consistently successful.

[MBjoern]

Good to know, thank you for your inputs