...
Looked at the signal ground of the 2m licor, with the oscilloscope probe ground connected to power ground. Saw hair-like spikes with a range of +- 1V at the bit frequency of the bitssignal. By shorting signal ground to power ground we could get rid of these spikes.
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card | SN |
|---|---|
viper | #7, 3284 |
emerald 0, EMM-8M | W250017 |
emerald 1, EMM-8M | W237191 |
power | W248060 |
This stack is now in box #8, which means it has a new Viasala barometer. rserial shows this is unit 9: B9 752.08 5.2\r\n
Barometer in box#1 was B7.
Tried increasing the sampling rates of the licors to 20 Hz, 19200 baud. The number of spurious interrupts increased to somewhere around 600+. The system was generally keeping up, as shown by data_stats, but sometimes things looked bad. So reduced the rates back to 10Hz, 9600 baud. The system runs well, with a background level of around 170 spurious interrupts/sec, as it was before this visit.
The licor message length is between 44 and 49 characters. So at 20Hz this is roughly 10bits * 49 * 20/sec = 9800 bits/sec, so we must use 19200 baud instead of 9600.
Conclusion: the problem with sampling Licors at 20Hz seems to be a data system issue, not an issue with the RS232 signals. Our simulation of this configuration in the lab did not include 5 TRHs (1 sample/sec), the barometer (1/sec) or the GPS (2 samples/sec).