Adhyyan Sekhsaria / MAX8U

A driver for the MAX8U GPS by uBlox. Provides core functionality. Communicates through I2C.

MAX8U Driver

This driver supports a wide range of functions provided by the MAX8U chip. Most of the essential features are supported. It lays a framework to add more commands easily, with only a little extra work.

Driver was originally made for the USC Rocket Propulsion Lab by Adhyyan Sekhsaria and Jamie Smith

Features

Currently supports:

• Getting coordinates in latitude, longitude, accuracy...
• Velocity measurements in each axis
• Individual satellite information
• Time of last message
• Antenna Power Status
• GPS Fix Quality
• Save configuration in memory

Documentation

Full documentation is available here

Usage

Code Structure:

In factory settings, the module is not configured to send any messages. For the GPS to give updates, we need to configure it by sending messages using setMessageEnabled() which internally calls sendMessage() and waitForAck().

calling configure() once will enable a few useful messages, and save this configuration in the MAX8U non-volatile memory.

update() to be called periodically by the user. Processes and reads all the messages currently stored in the GPS. Calls processMessage() on every message. processMessage(): processes the message currently in the buffer by calling the respective functions. Each message is read, and its relevant information is then stored in the public variables.

By default, the GPS sends messages in NMEA format (but we reconfigure it to UBX format), so readNextMessage() has to determine which format the message is.

define the macro MAX8U_DEBUG to enable printing out to message information to the debug port. If not defined, will only print error messages to the debug port.

Example

#include "MAX8U.h"

int main(){
    MAX8U gps(&pc, PIN_I2C_SDA, PIN_I2C_SCL, p25);
    bool booted = gps.begin();

    if(!booted){
        //handle error
    }
    booted = gps.configure();
    if(!booted){
        //handle error
    }

    while(true){
        bool newMessageRcvd = gps.update();
        pc.printf(">Position: %.06f %c, %.06f %c, Height %.02f m\r\n",
                  std::abs(gps.latitude), gps.latitude > 0 ? 'N' : 'S',
                  std::abs(gps.longitude), gps.longitude > 0 ? 'E' : 'W',
                  gps.height);

        // velocity
        pc.printf(">Velocity: %.02f m/s N, %.02f m/s E, %.02f m/s Down\r\n",
                  gps.northVel * .02f,
                  gps.eastVel * .02f,
                  gps.downVel * .02f);

        // accuracy
        pc.printf(">Fix: Quality: %" PRIu8 ", Num Satellites: %" PRIu8 ", Position Accuracy: %.02f m\r\n",
                static_cast<uint8_t>(gps.fixQuality), gps.numSatellites, gps.posAccuracy);

        // time
        pc.printf(">Time: %" PRIu8 "/%" PRIu8"/%" PRIu16" %" PRIu8":%" PRIu8 ":%" PRIu8 "\r\n",
                gps.month,
                gps.day,
                gps.year,
                gps.hour,
                gps.minute,
                gps.second);
    }
}