I'm working through just communicating AT commands though the serial ports (UART) with an Arduino UNO. I have no issues sending or receiving SMS with this new product.
Try a new SIM, and make sure your ISP supports these LTE bands:
Make sure your SMSC is factory default (make sure you haven't changed it). This only impacts sending SMS from what I've found. You can edit this with m-centre
It looks scarier than it is. You have to solder 4 cables (3 would be enough but thats another story) from a USB cable or buy that updater PCB. Then you need that firmware and a Windows Software from ublox.
Without the latest firmware you can receive one SMS per modem start with some carriers. The cut of the first character is a arduino core/basic functionality bug. I was able to pass it with a old core but you already tried this. You can also code the receiving SMS functionality for yourself and avoid the MKRNB lib but this is also a headache.
My hint: Update the modem firmware and the libs to the newest versions and try again. They fixed a lot of other issues with the modem with that firmware.
You start the SerialSARAPasstrough sketch from the MRNB lib tools and type ATI9 into the serial monitor.
I have been having the same issues, but I've found that if I comment out the following part of that example the messages are printed to the serial monitor including the first character. It would seem that the peek function isn't really peeking, or is moving the pointer forward one byte in the buffer.
// An example of message disposal
// Any messages starting with # should be discarded
if (sms.peek() == '#') {
Serial.println("Discarded SMS");
sms.flush();
}
I've tried a new IoT specific SIM and I still have the same issue
@intstarep My modem is now at L0.0.00.00.05.12 A.02.19 and the issue still remains
Edit:
I can now receive messages in the time frame of a few minutes.
This was a naive conclusion. Sometimes the time frame is > 10 min (never received. I gave up after this time)
Minmum (in my experience) for operation is 10 to 12.
My problem (and i think also yours) is that the carrier not enabled the LTE-M bands/protocol.
I think the 4G/5G/IoT/LTE-M/NB hype is not so hot as expected - so that's why here with me it's not enabled on every cell antenna - resulting in a weak signal. This might be also your problem-simple as that.
After running MKRNBScanNetworks which includes the scannerNetworks.getSignalStrength();, I got the following:
11:28:00.006 -> NB IoT/LTE Cat M1 networks scanner
11:28:11.443 -> Modem IMEI: xxxxxxxxxxxxxxxxxx
11:28:11.478 -> Current carrier: Telstra Telstra
11:28:11.516 -> Signal Strength: 99 [0-31]
11:28:11.552 -> Scanning available networks. May take some seconds.
11:31:11.448 ->
11:31:21.439 -> Current carrier:
11:34:21.334 -> Signal Strength: 13 [0-31]
11:34:21.334 -> Scanning available networks. May take some seconds.
11:35:38.113 -> > Telstra
11:35:38.113 ->
11:35:48.109 -> Current carrier: Telstra Telstra
11:35:48.109 -> Signal Strength: 13 [0-31]
11:35:48.146 -> Scanning available networks. May take some seconds.
11:38:48.023 ->
11:38:58.012 -> Current carrier:
11:41:57.889 -> Signal Strength: 12 [0-31]
11:41:57.889 -> Scanning available networks. May take some seconds.
11:43:23.687 -> > Telstra
11:43:23.687 ->
11:43:33.690 -> Current carrier: Telstra Telstra
11:43:33.690 -> Signal Strength: 12 [0-31]
11:43:33.724 -> Scanning available networks. May take some seconds.
11:46:33.592 ->
11:46:43.577 -> Current carrier:
11:49:43.437 -> Signal Strength: 12 [0-31]
11:49:43.437 -> Scanning available networks. May take some seconds.
11:51:06.203 -> > Telstra
11:51:06.203 ->
11:51:16.168 -> Current carrier: Telstra Telstra
11:51:16.205 -> Signal Strength: 13 [0-31]
11:51:16.205 -> Scanning available networks. May take some seconds.
My other board and antenna gives a similar result. I think the new SIM fixed the original problem, but now I'm limited by my signal strength.
The SIM is M2M only. Does this only use 2G and 3G networks? (Australia - Telstra)?
Is this the reason I have such bad signal strength?
No, LTE-M / NB is only 4G and 5G.
This signal strenght should be sufficient.
You can upload the serialSara sketch to the mkr1500 and then connect the USB of the board to a windows pc with the mConnect software from uBlox for debuging purposes.
99 means no signal/carrier, as you can see in the top-right corner. No operator means no sms...
What about taking the whole mess to another place with some signal to check your issues out?