add code example to MT6835 readme

Author: Richard Unger

src/encoders/mt6835/README.md

@@ -1,7 +1,5 @@
 # MT6835 SimpleFOC driver
 
-:warning: untested
-
 Driver for the MagnTek MT6835 precision magnetic rotary encoder.
 
 This sensor features support for up to 21 bit resolution (!) and speeds up to 120,000RPM. While its full precision requires calibration using an external calibration system, it is impressively precise even in uncalibrated state, and it offers an internal self-calibration mode whose precision is somewhere between the other two.
@@ -17,12 +15,50 @@ Connect the sensor to an SPI bus on your MCU. Pay attention to the voltage level
 Usage example:
 
 ```c++
-#include "Arduino.h"
-#include "Wire.h"
+#include <Arduino.h>
+
 #include "SimpleFOC.h"
 #include "SimpleFOCDrivers.h"
-#include "encoders/MT6835/MagneticSensorMT6835.h"
 
-// TODO code example
+#include "encoders/mt6835/MagneticSensorMT6835.h"
+
+#define SENSOR_nCS PB6
+
+SPISettings myMT6835SPISettings(1000000, MT6835_BITORDER, SPI_MODE3);
+MagneticSensorMT6835 sensor = MagneticSensorMT6835(SENSOR_nCS, myMT6835SPISettings);
+
+long ts;
+
+void setup() {
+    sensor.init();
+    ts = millis();
+}
+
+void loop() {
+    sensor.update();
+    long now = millis();
+    if (now - ts > 1000) {
+        ts = now;
+        SimpleFOCDebug::print("A: ");
+        SimpleFOCDebug::print(sensor.getAngle());
+        SimpleFOCDebug::print(" V: ");
+        SimpleFOCDebug::println(sensor.getVelocity());
+    }
+    delay(10);
+}
+
+```
+
+Set the zero position:
+
+```c++
+uint16_t pos = sensor.getZeroPosition();    // current value
+sensor.setZeroFromCurrentPosition();        // set zero to current position
+```
+
+Set the ABZ resolution (needed if you want to use ABZ as the default is 1):
+
+```c++
+sensor.setABZResolution(2048);
 ```