Saxion Lectoraat MT / AS5048

AS5048A SPI - Magnetic rotary encoder library

Library for communication over the SPI interface with the ams.com AS5048A magnetic rotary encoder.

Example:

Simple readout of a single angle measurement from a single sensor on the SPI-bus

#include "mbed.h"
#include <as5048spi.h>

// The sensors connection are attached to pins 5-8
As5048Spi sensor(p5, p6, p7, p8);
Serial pc(USBTX, USBRX); // tx, rx

int main() {
    while(1) {
        // 
        const int* angles = sensor.read_angle();
        int angle = angles[0];
        
        // The read angle returns the value returned over the SPI bus, including parity bit
        pc.printf("Read result: %x\r\n", angle);
        
        if( As5048Spi::parity_check(angle) )
        {
            // Convert range from 0 to 2^14-1 to 0 - 360 degrees
            int degrees = As5048Spi::degrees(angle)/100;
            pc.printf("Parity check succesfull.\r\n");
            pc.printf("Angle: %i degrees\r\n", degrees );
        }
        else
        {
            pc.printf("Parity check failed.\r\n");
        }
            
        wait_ms(500);
    }
}

The class supports daisy chaining multiple sensors on the SPI-bus as well. See: SPI-Daisy-Chaining.

as5048spi.h

Committer:
JSpikker
Date:
2014-09-18
Revision:
0:3edcf58e51e7
Child:
2:2958500883e0

File content as of revision 0:3edcf58e51e7:

#include "mbed.h"
typedef enum {
    AS_FLAG_PARITY = 0x8000,
    AS_FLAG_READ = 0x4000,
} As5048Flag;

typedef enum {
    AS_CMD_NOP = 0x0000,
    AS_CMD_ERROR = 0x0001 | AS_FLAG_READ, // Reads error ireguster and clear error flags
    AS_CMD_DIAGNOSTICS = 0x3FFD |  AS_FLAG_READ, // Reads automatic gain control and diagnostics info
    AS_CMD_MAGNITUDE = 0x3FFE | AS_FLAG_READ,
    
    AS_CMD_ANGLE = 0x3FFF| AS_FLAG_PARITY | AS_FLAG_READ,
} As5048Command;



class As5048Spi
{
public:
    As5048Spi(PinName mosi, PinName miso, PinName sclk, PinName chipselect, int nDevices = 1);
    ~As5048Spi();
    
    bool error(int device = -1);
    void frequency(int frequency = 1000000);
    const int* read(As5048Command command);
    const int* read_sequential(As5048Command command);
    
    const int* read_angle();
    const int* read_angle_sequential();

    
    static int mask(int sensor_result);
   
    static bool parity_check(int sensor_result);
    static int degrees(int sensor_result);
    static int radian(int sensor_result);
    

protected:
    int _nDevices;
    DigitalOut _chipSelectN;
    SPI _spi;
    
    int* _readBuffer; // Stores the results of the last sequential read
    
    int* _read(As5048Command command);
};