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:
3:a8ad32e439d4
Parent:
2:2958500883e0
Child:
4:06b89a41109e
--- a/as5048spi.h	Thu Dec 04 10:00:42 2014 +0000
+++ b/as5048spi.h	Tue Mar 17 14:46:45 2015 +0000
@@ -6,7 +6,7 @@
 
 typedef enum {
     AS_CMD_NOP = 0x0000,
-    AS_CMD_ERROR = 0x0001 | AS_FLAG_READ, // Reads error ireguster and clear error flags
+    AS_CMD_ERROR = 0x0001 | AS_FLAG_READ,       // Reads error register of sensor 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,
     
@@ -29,8 +29,18 @@
     ~As5048Spi();
     
     bool error(int device = -1);
+    
+    /// Sets the SPI clock frequency in Hz. Maximum tested frequency is 10MHz.
     void frequency(int frequency = 1000000);
+    
+    /// Sends a read command to the sensor.
     const int* read(As5048Command command);
+    
+    /// Sends a read command to the sensor. 
+    /// A call to this function will not directly return the requested value. The
+    /// requested value will be returned in a next read_sequential call. 
+    /// Use this function to read sensor values with minimum speed impact on SPI-bus
+    /// and microcontroller.
     const int* read_sequential(As5048Command command);
     
     /// Performs a single angle measurement on all sensors
@@ -49,11 +59,19 @@
 
     /// Returns lowest 14-bits
     static int mask(int sensor_result);
+
+    /// Applies the mask to the first n bytes in the read buffer (for daisychained sensors).
     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);
+    
+    /// Returns an angle from 0 to 36000 (degrees times 100).
+    /// @param sensor_result is one of the values returned by read_angle or read_angle_sequential
     static int degrees(int sensor_result);
+    
+    /// Returns an angle from 0 to 2*PI*100 
+    /// @param sensor_result is one of the values returned by read_angle or read_angle_sequential
     static int radian(int sensor_result);