To use the LoRa TDOA + WiFi lookup, you must pass WiFi access points in a specific format from your decoder payload function:
{
"access_points": [
{
"bssid": "01:02:03:04:05:06",
"rssi": -45
},
{
"bssid": "aa:bb:cc:dd:ee:ff",
"rssi": -63
},
{
"bssid": "06:05:04:03:02:01",
"rssi": -56
}
]
}
You can return any other payload fields too; only access_points is used for the Collos integration.
Example #
Say your device scans WiFi access points and sends them over LoRaWAN FPort 2, with six bytes per BSSID and one byte indicating the RSSI:
01 02 03 04 05 06 D3 AA BB CC DD EE FF C1 06 05 04 03 02 01 C8
You can decode this using the following payload function:
// pad16 converts decimal to hex with leading zero
function pad16(b) {
var h = b.toString(16);
return (h + "").length < 2 ? "0" + h : h;
}
// Decoder decodes bytes in payload fields
function Decoder(bytes, port) {
var result = {};
switch (port) {
case 1:
// parse bytes on FPort 1
break;
case 2:
// parse access points on FPort 2
result.access_points = [];
// read by 7 bytes (6 for BSSID + 1 for RSSI)
for (var i = 0; i < bytes.length; i += 7) {
// read the BSSID and format as hex with colons
var bssid = bytes.slice(i, i + 6).map(pad16).join(":");
// read the RSSI (convert from uint8 to int8)
var rssi = bytes[i + 6] - 0x100;
// add the access point
result.access_points.push({
bssid: bssid,
rssi: rssi
});
}
break;
}
return result;
}