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.cpp
- Committer:
- JSpikker
- Date:
- 2015-03-17
- Revision:
- 4:06b89a41109e
- Parent:
- 2:2958500883e0
File content as of revision 4:06b89a41109e:
#include "as5048spi.h" As5048Spi::As5048Spi(PinName mosi, PinName miso, PinName sclk, PinName chipselect, int ndevices) : _nDevices(ndevices), _chipSelectN(chipselect), _spi(mosi, miso, sclk) { _chipSelectN.write(1); // AS5048 needs 16-bits for is commands // Mode = 1: // clock polarity = 0 --> clock pulse is high // clock phase = 1 --> sample on falling edge of clock pulse _spi.format(16, 1); // Set clock frequency to 1 MHz (max is 10Mhz) _spi.frequency(1000000); _readBuffer = new int[ndevices]; } As5048Spi::~As5048Spi() { delete [] _readBuffer; } int As5048Spi::degrees(int sensor_result) { return mask(sensor_result) * 36000 / 0x4000; } int As5048Spi::radian(int sensor_result) { return mask(sensor_result) * 62832 / 0x4000; } bool As5048Spi::error(int device) { if( device == -1 ) { for(int i = 0; i < _nDevices; ++i) { if( _readBuffer[i] & 0x4000 ) { return true; } } } else if( device < _nDevices ) { return (_readBuffer[device] & 0x4000) == 0x4000; } return false; } void As5048Spi::frequency(int hz) { _spi.frequency(hz); } int As5048Spi::mask(int sensor_result) { return sensor_result & 0x3FFF; // return lowest 14-bits } void As5048Spi::mask(int* sensor_results, int n) { for(int i = 0; i < n; ++i) { sensor_results[i] &= 0x3FFF; } } bool As5048Spi::parity_check(int sensor_result) { // Use the LSb of result to keep track of parity (0 = even, 1 = odd) int result = sensor_result; for(int i = 1; i <= 15; ++i) { sensor_result >>= 1; result ^= sensor_result; } // Parity should be even return (result & 0x0001) == 0; } const int* As5048Spi::read(As5048Command command) { _read(command); // Send command to device(s) return _read(AS_CMD_NOP); // Read-out device(s) } const int* As5048Spi::read_sequential(As5048Command command) { return _read(command); } const int* As5048Spi::read_angle() { _read(AS_CMD_ANGLE); // Send command to device(s) return _read(AS_CMD_NOP); // Read-out device(s) } const int* As5048Spi::read_angle_sequential() { return _read(AS_CMD_ANGLE); } int* As5048Spi::_read(As5048Command command) { if(_nDevices == 1) { // Give command to start reading the angle _chipSelectN.write(0); wait_us(1); // Wait at least 350ns after chip select _readBuffer[0] = _spi.write(command); _chipSelectN.write(1); wait_us(1); // Wait at least 350ns after chip select } else { // Enable the sensor on the chain _chipSelectN.write(0); wait_us(1); // Wait at least 350ns after chip select for(int i = 0; i < _nDevices; ++i) { _readBuffer[i] = _spi.write(command); } _chipSelectN.write(1); wait_us(1); // Wait at least 350ns after chip select } return _readBuffer; }