Imp C001 breakout - great!


#1

Just today receive cellular C001 breakout board.
Blink-up was easy (except that antenna plug) and fine, in a bit longer as WiFi blink-up.
Quick well-known imp web-server example (directly copy-paste from imp webpage, just change I2C RH-T sensor pins as told) works as expected.
I have no idea what cellular network was in use - Latvian Mobile phone (in general Telia) or Tele2 - and seems that it’s not important.
So in Riga, Latvia cellular C001 work fine, as imp001 do in 2012.
Great job! Thanks to all imp team!


#2

The first connect is always a little slow - usually it’s about 40-50 seconds to cold boot the modem and attach to a network, then do the secure imp connection.

You can find the cellular network in use like this:

local iface = imp.net.info().interface[0];
if ("rssi" in iface) server.log("rssi = "+iface.rssi);
if ("cellinfo" in iface) server.log("cellinfo = "+iface.cellinfo);

Cellinfo include the MCC/MNC of the network, cell ID, etc. It looks like this:

4G,6300,20,10,10,FDD,234,10,2046,7D5001E,482,18,-105,-10.0,NOCONN

Here, 234,10 are the network (O2 UK in this case, see http://www.mcc-mnc.com/ to look them up)


#3

Thanks Hugo! Got it!


#4

Echoing PeterAP, blinkup worked well, and the simple webserver app runs with just that one mod.

I do have a question about the onboard LED; when I paste in the example code found at
developer.electricimp.com/hardware/resources/reference-designs/impc001breakout
it compiles without error, but the LED does not flash.

Is it possible that the SPI port implemented in the HW has changed since the sample code was posted?
(my breakout board rev is 4.2 20180713)

In general, the startup guide was very clear and the steps were easy to follow. This is looking like a
really great product.


#5

Ah, the example does not include turning the power gate on. I’ve updated the example, but just add:

// Turn on power to peripherals
hardware.pinYG.configure(DIGITAL_OUT, 1);

…to the top of your code and try again?


#6

Yup, that did it.

Thanks, Hugo, you guys rock!


#7

Can I get a sense of the strength of the C001 cellular connection from imp.net.info? Like bars on my cellphone?


#8

Yes, though it’s a little complex especially on LTE.

imp.net.info() returns network info for cellular, just as it does for other network types.

On 2G and 3G, RSSI (received signal strength indicator) provides a good indicator of the connection quality. Typically:

-79dBm or higher is 5 bars
-89dBm to -80dBm is 4 bars
-99dBm to -90dBm is 3 bars
-106dBm to -100dBm is 2 bars
Below -106dBm (but still connected) is 1 bar.

On LTE there are two metrics which are a little hard to combine, RSRP (reference signal received power) and RSRQ (reference signal received quality). One of the better descriptions I’ve seen is here https://s4gru.com/entry/308-rssi-vs-rsrp-a-brief-lte-signal-strength-primer/

Looking just at RSRP, you can vaguely say that higher than -85dBm is great, between -100dBm and -86dBm is good, between -111dBm and -101dBm is fair and below that is poor… but you can still have a low RSRP but decent throughput.