This script will blink the FiPy led in colors that indicate LTE signal quality. Green is the reference value, colors going towards blue represent a weaker signal, yellow or red tones represent stronger signals. There are two blinks, the first indicates RSRP and the second RSRQ. For a discussion of these parameters see (https://www.mdpi.com/1424-8220/20/6/1636/htm).
As default values, the follwing windows for the parameters (as defined by their center and half width values in function signal_quality()) are used:
RSRP [ -140 dBm, -90 dBm] center: -110.0 dBm
RSRQ [ -22.5 dB, -7.5 dB] center: -15.0 dB
That means that the led is green when the signal is on the center value, blue when the minimal value is obtained and red when the maximal value is returned.
Values outside of the ranges are treated like the max/min values. When the range is smaller, sensitivity around the center is increased.
In order to "calibrate" your ltesignal device, leave it connected
with the console and run it at a location with "normal" or
"reference" signal. Leave it running for a while (a couple of
minutes) and use the last two values of the last data row (mean
values <rsrp> and <rsrq>)
rsrp,rsrq,<rsrp>,<rsrq> -107.29 -14.44 -107.7893 -14.724375
as new center values by setting
signal_quality(rsrp_center=-107.8, rsrq_center=-14.7, show_status=True)
in the main program. The new reference value will now be shown as pure green, a better signal will give more yellowish/redish color tones, a worser signal gives green with blue tones or blue.
For my antenna (pycom 2016.08.18 rev.02) and location (a small town close to Seville, Spain), values are around -108 dBm and -15 dB at my working place which is just on the verge of dropping data.
The modem command does not always return signal strength values, so longer pauses between the blinking of the leds are normal. It would be easy to add a wifi access point to the code so you can see the precise values that are printed to the log with a telnet session. You could also easily send them online.
I am just starting to learn LTE so I don't know if this program incurs data usage, be careful just in case.
Disable pybytes at startup:
import pycom
pycom.pybytes_on_boot(False)
SIM-cards: I have the Vodafone LTE card that pycom sells. If you have another
SIM you should comment the two socket.dnsserver() calls in line 4 and 5 of
main.py. Also, enter the correct band and apn parameters in the call
lte.attach().
Have fun!