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.

Diff: as5048spi.h

Revision:
2:2958500883e0
Parent:
0:3edcf58e51e7
Child:
3:a8ad32e439d4
--- a/as5048spi.h	Thu Sep 18 19:28:25 2014 +0000
+++ b/as5048spi.h	Thu Dec 04 10:00:42 2014 +0000
@@ -13,6 +13,13 @@
     AS_CMD_ANGLE = 0x3FFF| AS_FLAG_PARITY | AS_FLAG_READ,
 } As5048Command;
 
+// Masks for bits in the result of the AS_CMD_DIAGNOSTICS command
+typedef enum {
+    AS_DIAG_CORDIC_OVERFLOW = 0x0200,
+    AS_DIAG_HIGH_MAGNETIC = 0x0400,
+    AS_DIAG_LOW_MAGNETIC = 0x0800,
+} As5048Diagnostics;
+
 
 
 class As5048Spi
@@ -26,12 +33,25 @@
     const int* read(As5048Command command);
     const int* read_sequential(As5048Command command);
     
+    /// Performs a single angle measurement on all sensors
+    /// @return Array of raw angle data. To get the 14-bit value representing
+    ///     the angle, apply the mask() to the result.
+    ///     To get an angle in degrees divide 360 by the result of the call to mask().
     const int* read_angle();
+    
+    /// Performs sequential angle measurements on all sensors. The first time this
+    /// method is called the result is not usefull, the measurement data of the call
+    /// will be returned by the next call to this method.
+    /// @return Array of raw angle data. To get the 14-bit value representing
+    ///     the angle, apply the mask() to the result.
+    ///     To get an angle in degrees divide 360 by the result of the call to mask().
     const int* read_angle_sequential();
 
-    
+    /// Returns lowest 14-bits
     static int mask(int sensor_result);
-   
+    static void mask(int* sensor_results, int n);
+    /// Checks if the return value from the sensor has the right parity
+    /// @return true if ok
     static bool parity_check(int sensor_result);
     static int degrees(int sensor_result);
     static int radian(int sensor_result);