Mbed OS v5.x Network Interface driver for Quectel BG96

Specifying library configuration and settings

The following settings configure the I/O settings for the BG96 Driver. The current settings are for the AVNET RSR1157 NbIOT BG96 expansion board. If you use a different board, the settings maydiffer.

{
    "name": "BG96_library",
    "config": {
       "bg96_reset": {
           "help": "RESET pin for the BG96",
           "value": "D7"
       },
       "bg96_wake": {
           "help": "Wake pin to BG96",
           "value": "D11"
       },
       "bg96_pwrkey": {
           "help": "pwr key input to BG96",
           "value": "D10"
       },
       "bg96_tx": {
           "help": "TX pin for serial connection to BG96",
           "value": "D8"
       },
       "bg96_rx": {
           "help": "RX pin for serial connection to BG96",
           "value": "D2"
       }
    }
}

Specifing the application configuration settings

In the mbed_app.json file that is used with this driver, the following settings are needed.

{
    "macros": ["DEFAULT_APN=\"m2m.com.attz\""
              ],
    "config": {
       "bg96_debug": {
           "help" : "enable or disable WNC debug messages.",
           "value": 0
       },
       "bg96-debug-setting": {
           "help" : "bit value 1 and/or 2 enable WncController debug output, bit value 4 enables mbed driver debug output.",
           "value": "0x84"
       }
    },
    "target_overrides": {
        "*": {
            "platform.stdio-baud-rate": 115200,
            "platform.stdio-convert-newlines": true
        }
    }
}

Default APN

The macro DEFAULT_APN is the APN that will be used when the connect method is called with no argments (if you don't specify an APN in your code).

Debug settings

The bg96_debug setting enables or disabled debug output from the driver.

The bg96-debug-settings allow you to select various types of debug output. It is a bit-field with the following settings:

 0x04 - Driver Enter/Exit debug information
 0x08 - Driver Event Queue debug information
 0x20 - Dump Driver Arrays
 0x80 - Trace AT command execution

Overriding settings

The driver is designed to use a baud rater of 115200 so this must be specified (it will default to 9600 otherwise). The convert-newlines helps terminal output format by removing the requirment to modify the terminal program settings.

GNSS Add-ons

This version of the driver adds GNSS capabilities. It is not using the usbnmea port of the BG96 modem to get the NMEA phrases, but relying on reading the GNSS data by issuing AT commands.

TLS Socket Add-on

An API is added to the BG96Interface in order to instantiate and obtain a reference to a BG96TLSSocket. A BG96TLSSocket allows the application to open a TLS connection using the BG96 TLS capabilities of the BG96 modem. This unloads the processor from running the TLS algorithms and allow lower memory devices to be used.

API Get a BG96TLSSocket instance:

BG96Interface bg96;
BG96TLSSocket * tls_socket = bg96.getBG96TLSSocket();

The BG96Socket provides the following interface:

const char cacert = "...."; // stringified CA certificate
const char hostname = "..."; // hostname or CDN of server
int port = 8883;
char buf[512];
strcpy(buf, message_to_send);
tls_socket.set_ca_cert(&cacert[0]); 
tls_socket.set_option(BG96TLS_SSLVERSION, SSLVERSION_TLS2); //See list in header
tls_socket.open(hostname, port);
tls_socket.send(buf, len(buf));
char * recvbuf = &buf[0];
while(tls_socket.recv(recvbuf, CHUNK_SIZE)) {
    recvbuf += CHUNK_SIZE;
}
printf("received %s\r\r", &buf[0]);
tls_socket.close();

Delete the BG96TLSSocket:

bg96.discardBG96TLSSocket(tls_socket);

or simply

delete(tls_socket);

Interstingly, the BG96TLSSocket implements the TLSSocket public interface, meaning that it can be used by software relying on TLSSocket to function.

TLSSocket * a_tls_socket = (TLSSocket*) tls_socket;

Do whatever required with a_tls_socket.