OptFlow: correct SPI mode and baud rates

libraries/AP_HAL_AVR/SPIDeviceManager_APM2.cpp

@@ -42,7 +42,7 @@ void APM2SPIDeviceManager::init(void* machtnichts) {
     AVRDigitalSource* optflow_cs = new AVRDigitalSource(_BV(3), PF);
     /* optflow: divide clock by 8 to 2Mhz
      * spcr gets bit SPR0, spsr gets bit SPI2X */
-    _optflow_spi0 = new AVRSPI0DeviceDriver(optflow_cs, _BV(SPR0), _BV(SPR0), _BV(SPI2X));
+    _optflow_spi0 = new AVRSPI0DeviceDriver(optflow_cs, _BV(SPR0)|_BV(CPOL)|_BV(CPHA), _BV(SPR0)|_BV(CPOL)|_BV(CPHA), _BV(SPI2X));
     _optflow_spi0->init();
 
     /* Dataflash CS is on Arduino pin 28, PORTA6 */
@@ -53,8 +53,10 @@ void APM2SPIDeviceManager::init(void* machtnichts) {
     _dataflash = new AVRSPI3DeviceDriver(df_cs, 0, 0);
     _dataflash->init();
 
-    /* XXX need correct mode and baud */
-    _optflow_spi3 = new AVRSPI3DeviceDriver(optflow_cs, 0, 0);
+    /* optflow uses mode 3 and a clock of 2mhz
+     * ucsr3c = _BV(UCPHA3N)|_BV(UCPOL3) = 3
+     * ubrr3 = 3 */
+    _optflow_spi3 = new AVRSPI3DeviceDriver(optflow_cs, 3, 3);
     _optflow_spi3->init();
 }