Handy utility functions for the Particle Electron cellular device
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rickkas7 Version 0.0.7
Added getCREG and isLTE() calls.
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README.md

Cellular Helper

A library to access useful things from the Electron cellular modem

This library uses the Logging functionality, so it can only be used with system firmware 0.6.0 and later. It also can only be used on an Electron, not a Photon/P1/Core, for obvious reasons.

Simple functions

The simple information calls query information from the modem and return a String.

Log.info("manufacturer=%s", CellularHelper.getManufacturer().c_str());

Log.info("model=%s", CellularHelper.getModel().c_str());

Log.info("firmware version=%s", CellularHelper.getFirmwareVersion().c_str());

Log.info("ordering code=%s", CellularHelper.getOrderingCode().c_str());

Log.info("IMEI=%s", CellularHelper.getIMEI().c_str());

Log.info("IMSI=%s", CellularHelper.getIMSI().c_str());

Log.info("ICCID=%s", CellularHelper.getICCID().c_str());

These are all just various bits of data from the modem or the SIM card.

0000008020 [app] INFO: manufacturer=u-blox
0000008040 [app] INFO: model=SARA-U260
0000008060 [app] INFO: firmware version=23.20
0000008090 [app] INFO: ordering code=SARA-U260-00S-00

You might find the ICCID (SIM Number) to be useful as well.

Cellular.on needs to have been called, which will be for automatic mode.

Note that if you are using threaded mode with semi-automatic or manual mode you must also wait after turning the modem on. 4 seconds should be sufficient, because Cellular.on() is asynchronous and there's no call to determine if has completed yet.

Cellular connection functions

These functions can only be used after connecting to the cellular network.

getOperatorName

Returns a string containing the operator name, for example AT&T or T-Mobile in the United States.

Log.info("operator name=%s", CellularHelper.getOperatorName().c_str());

Example output:

0000008574 [app] INFO: operator name=AT&T

getRSSIQual

Returns the RSSI (signal strength) value and a quality value.

CellularHelperRSSIQualResponse rssiQual = CellularHelper.getRSSIQual();
int bars = CellularHelperClass::rssiToBars(rssiQual.rssi);

Log.info("rssi=%d, qual=%d, bars=%d", rssiQual.rssi, rssiQual.qual, bars);
0000008595 [app] INFO: rssi=-75, qual=2, bars=3

The RSSI is in dBm, the standard measure of signal strength. It's a negative value, and values closer to 0 are higher signal strength.

The quality value is 0 (highest quality) to 7 (lowest quality) or 99 if the value unknown. It's typically 99 for 2G connections. The qual value is described in the u-blox documenation, and it's returned by the call, but you probably won't need to use it.

The rssiToBars() method converts the RSSI to a 0 to 5 bars, where 5 is the strongest signal.

getEnvironment

The method getEnvironment returns cell tower information. The is the u-blox AT+CGED comamnd.

CellularHelperEnvironmentResponseStatic<8> envResp;

CellularHelper.getEnvironment(CellularHelper.ENVIRONMENT_SERVING_CELL_AND_NEIGHBORS, envResp);
if (envResp.resp != RESP_OK) {
	// We couldn't get neighboring cells, so try just the receiving cell
	CellularHelper.getEnvironment(CellularHelper.ENVIRONMENT_SERVING_CELL, envResp);
}
envResp.logResponse();

The first line declares a variable to hold up to 8 neighbor towers.

The first getEnvironment call tries to get the serving cell (the one you're connected to) and the neighbor cells. This only works for me on the 2G (G350) Electron.

If that fails, it will try again only using the serving cell information.

This sample just prints the information to serial debug:

0000008645 [app] INFO: service rat=UMTS mcc=310, mnc=410, lac=2cf7 ci=8a5a782 band=UMTS 850 rssi=0 dlf=4384 ulf=4159

Note that the rssi will always be 0 for 3G towers. This information is only returned by the AT+CGED command for 2G towers. You can use getRSSIQual() to get the RSSI for the connected tower; that works for 3G.

getLocation

This function returns the location of the Electron, using cell tower location. This call may take 10 seconds to complete!

CellularHelperLocationResponse locResp = CellularHelper.getLocation();
Log.info(locResp.toString());

The locResp contains the member variables:

  • lat - The latitude (in degrees, -90 to +90)
  • lon - The longitude (in degrees, -180 to +180)
  • alt - The altitude (in meters)
  • uncertainty - The radius of the circle of uncertainty (in meters)

Miscellaneous Utilities

These are just handy functions.

ping

Uses the ping function (ICMP echo) to determine if a server on the Internet is accessible. Not all servers respond to ping. The function returns true if the ping is responded to. Only one attempt is made.

Log.info("ping 8.8.8.8=%d", CellularHelper.ping("8.8.8.8"));

Result:

0000014927 [app] INFO: ping 8.8.8.8=1

dnsLookup

This does a DNS (domain name service) hostname lookup and returns an IP address for that server.

Log.info("dns device.spark.io=%s", CellularHelper.dnsLookup("device.spark.io").toString().c_str());

Result:

0000015857 [app] INFO: dns device.spark.io=54.225.2.62

If the host name cannot be resolved (does not exist or no DNS available) then the empty IP address is returned. This can be tested for by checking:

if (addr)

Or when printed as above, will be 0.0.0.0.

Examples

1-Simple Demo

The simple demo tests all of the basic functions in the library, displaying the results to USB serial.

The code examples in this document were taken from this example.

2-Show Carriers Demo

This is a demo program that uses the cellular modem to scan for available operators, frequency band used, and signal strength. It prints a result like this to USB serial:

3G AT&T UMTS 850 2 bars (310410)
2G T-Mobile DCS 1800 or 1900 2 bars (310260)

It should work even when you can't connect to a tower and also display carriers that are not supported by your SIM. (It only displays carriers compatible with the GSM modem, however, so it won't, for example, display Verizon in the United States since that requires a PCS modem.)

This is a very time consuming operation (it can take 2 minutes or longer to run) and it's pretty rarely needed, so it builds on the CellularHelper library but the commands it uses (COPS and COPN) are not part of the library itself because they're so rarely needed.

To build a binary for this, you can download the repository and use the Particle CLI compiler from the top level of it:

particle compile electron examples/2-show-carriers/ --saveTo firmware.bin --target 0.6.0

Then you can flash it to your Electron in DFU mode (blinking yellow):

particle flash --usb firmware.bin

3-Select Carrier Demo

The 3-select-carrier example shows how to prefer a certain carrier when multiple carriers are supported by the SIM card.

  • You should use SYSTEM_MODE(SEMI_AUTOMATIC) so you can set the carrier before trying to connect.
  • You need to turn the cellular modem on using cellular_on(NULL) or Cellular.on() (see comments in the code).
  • Call selectOperator() with the MCC/MNC. For example:
	// Select the operator using the MCC/MNC string. For example:
	// "310410" = AT&T
	// "310260" = T-Mobile
	bool bResult = CellularHelper.selectOperator("310260");

The 2-show-carriers example prints out the MCC/MNC for carriers at your location.

  • If the operator needs to be changed, it may take around 20 seconds to do so. If the operator is already selected, it returns more or less immediately.
  • The setting of the operator is stored in the modem, but is reset on power down, so you should always select the operator in setup().

On a cold boot, you might see something like this in the USB serial debug log:

     5.297 AT send      12 "AT+UDOPN=0\r\n"
     5.307 AT read ERR  34 "\r\n+CME ERROR: no network service\r\n"
     5.307 AT send      22 "AT+COPS=4,2,\"310260\"\r\n"
    23.778 AT read OK    6 "\r\nOK\r\n"
0000023789 [app] INFO: selectOperator returned 1

Then, later:

0000042189 [system] INFO: ARM_WLAN_WD 2
0000042189 [system] INFO: CLR_WLAN_WD 1, DHCP success
    42.180 AT send      12 "AT+UDOPN=9\r\n"
    42.220 AT read  +   24 "\r\n+UDOPN: 2,\"T-Mobile\"\r\n"
    42.230 AT read OK    6 "\r\nOK\r\n"
0000042241 [app] INFO: current operator=T-Mobile

If you do a warm boot after setting:

     2.507 AT send      12 "AT+UDOPN=0\r\n"
     2.517 AT read  +   22 "\r\n+UDOPN: 0,\"310260\"\r\n"
     2.527 AT read OK    6 "\r\nOK\r\n"
0000002527 [app] INFO: operator already 310260
0000002527 [app] INFO: selectOperator returned 1

4-Test CREG

Simple test of the CREG command, used to get the CI and LAC information on LTE devices (SARA-R410). It also works on the SARA-U and SARA-G.

Version History

0.0.7 (2018-11-27) Added the getCREG call 0.0.6 Added selectOperator