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GPS NEO-M8n

Today I do use the Neo M8n GPS receiver. I was not happy with the Neo 6 and Neo 7 series as they only have a battery back-uped RAM and I kept loosing data no matter what. And I did not wanted to initialize the device at each start up.

So the NEO-M8n uses a flash RAM. I do Programm the GPS with the configuration SW provided by U-blox (U-Center).

Using  a NEMA protocol as the output standard would make you use a NEMA protocol parser to filter out the desired data. A parser is needed because the amount of data transmitted can vary.

I did turn off the NEMA protocol and only use U-blox’s own UBX protocoll. Because the amount of bytes in this protocoll is fix (thx U-blox ;-)), you can simply pick the bytes at a given position to retrieve your information. Easy.

POSLLH uses 28bytes and VELNED uses 36bytes. Latitude, longitude, altitude, heading and ground velocity is available.
Here’s the code:

 
/***********************************************************************************
 * The gps data received by the UART are stored away. We use a NEO-M8n from ublock
 * with NEMA protocol turned off. Instead the ublock protocol UBX is used to get
 * well defined number of bytes that can be read
 ***********************************************************************************/
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	if (huart->Instance == UART4)
	{
		parseFlightMonitorData();
	}

	if (huart->Instance == UART5)
	{
		latitude[0] = GPS_BUF[14];
		latitude[1] = GPS_BUF[15];
		latitude[2] = GPS_BUF[16];
		latitude[3] = GPS_BUF[17];

		longitude[0] = GPS_BUF[10];
		longitude[1] = GPS_BUF[11];
		longitude[2] = GPS_BUF[12];
		longitude[3] = GPS_BUF[13];

		hMSLGPS[0] = GPS_BUF[22];
		hMSLGPS[1] = GPS_BUF[23];
		hMSLGPS[2] = GPS_BUF[24];
		hMSLGPS[3] = GPS_BUF[25];

		groundSpeedGPS[0] = GPS_BUF[60];
		groundSpeedGPS[1] = GPS_BUF[61];
		groundSpeedGPS[2] = GPS_BUF[62];
		groundSpeedGPS[3] = GPS_BUF[63];

		headingGPS[0] = GPS_BUF[64];
		headingGPS[1] = GPS_BUF[65];
		headingGPS[2] = GPS_BUF[66];
		headingGPS[3] = GPS_BUF[67];

		gpsDataReady = SET;
	}
}