LibrePilot/flight/AHRS/ahrs.c

/**
 ******************************************************************************
 * @addtogroup AHRS AHRS Control
 * @brief The AHRS Modules perform
 *
 * @{ 
 * @addtogroup AHRS_Main
 * @brief Main function which does the hardware dependent stuff
 * @{ 
 *
 *
 * @file       ahrs.c
 * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
 * @brief      INSGPS Test Program
 * @see        The GNU Public License (GPL) Version 3
 * 
 *****************************************************************************/
/* 
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 3 of the License, or 
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
 * for more details.
 * 
 * You should have received a copy of the GNU General Public License along 
 * with this program; if not, write to the Free Software Foundation, Inc., 
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */


/* OpenPilot Includes */
#include "ahrs.h"
#include "pios_opahrs_proto.h"
#include "ahrs_fsm.h"		/* lfsm_state */

/**
 * State of AHRS EKF
 * @arg AHRS_IDLE - waiting for data to be available for filtering
 * @arg AHRS_DATA_READY - Data ready for downsampling and processing
 * @arg AHRS_PROCESSING - Performing update on the available data
 */
enum {AHRS_IDLE, AHRS_DATA_READY, AHRS_PROCESSING} ahrs_state;

/**
 * @addtogroup AHRS_ADC_Configuration ADC Configuration
 * @{
 * Functions to configure ADC and handle interrupts
 */
void AHRS_ADC_Config(int32_t ekf_rate, int32_t adc_oversample);
void AHRS_ADC_DMA_Handler(void);
void DMA1_Channel1_IRQHandler() __attribute__ ((alias ("AHRS_ADC_DMA_Handler")));
/**
 * @}
 */

/**
 * @addtogroup AHRS_Definitions 
 * @{
 */
#define EKF_RATE                50
#define ADC_OVERSAMPLE          10
#define ADC_CONTINUOUS_CHANNELS PIOS_ADC_NUM_PINS
#define PREDICTION_COUNT        4

// TODO: Define calibration procedure including changes over temperature
#define VDD            3.3    /* supply voltage for ADC */
#define FULL_RANGE     4096   /* 12 bit ADC */
#define ACCEL_RANGE    2      /* adjustable by FS input */
#define ACCEL_GRAVITY  9.81   /* m s^-1 */
#define ACCEL_SENSITIVITY    ( VDD / 5 )
#define ACCEL_SCALE    ( (VDD / FULL_RANGE) / ACCEL_SENSITIVITY * 2 / ACCEL_RANGE * ACCEL_GRAVITY )
#define ACCEL_OFFSET  -2048  

#define GYRO_SENSITIVITY   ( 2.0 / 1000 ) /* V sec deg^-1 */
#define RAD_PER_DEGREE     ( 3.14159 / 180 )
#define GYRO_SCALE         ( (VDD / FULL_RANGE) / GYRO_SENSITIVITY * RAD_PER_DEGREE )
#define GYRO_OFFSET       -1675 /* From data sheet, zero accel output is 1.35 v */

/**
 * @addtogroup AHRS_Local Local Variables 
 * @{
 */
struct mag_sensor {
  uint8_t id[4];
  struct {
    int16_t axis[3];
  } raw;
};

struct accel_sensor {
  struct {
    uint16_t x;
    uint16_t y;
    uint16_t z;
  } raw;
  struct {
    float x;
    float y;
    float z;
  } filtered;
};

struct gyro_sensor {
  struct {
    uint16_t x;
    uint16_t y;
    uint16_t z;
  } raw;
  struct {
    float x;
    float y;
    float z;
  } filtered;  
  struct {
    uint16_t xy;
    uint16_t z;
  } temp;
};

struct attitude_solution {
  struct {
    float q1;
    float q2;
    float q3;
    float q4;
  } quaternion;

  struct {
    float roll;
    float pitch;
    float yaw;
  } euler;
};
/**
 * @}
 */

struct altitude_sensor {
  float altitude;
  float pressure;
  float temperature;
};

static struct mag_sensor        mag_data;
static struct accel_sensor      accel_data;
static struct gyro_sensor       gyro_data;

static struct altitude_sensor   altitude_data;

static struct attitude_solution attitude_data = {
  .quaternion = {
    .q1 = 1.011,
    .q2 = 2.022,
    .q3 = 3.033,
    .q4 = 0,
  },
  .euler = {
    .roll  = 4.044,
    .pitch = 5.055,
    .yaw   = 6.066,
  },
};

/* Function Prototypes */
void process_spi_request(void);
void downsample_data();

/**
 * @addtogroup AHRS_Global_Data AHRS Global Data
 * @{
 * Public data.  Used by both EKF and the sender
 */
int16_t fir_coeffs[ADC_OVERSAMPLE+1];          // FIR filter coefficients
int16_t raw_data_buffer[ADC_CONTINUOUS_CHANNELS * ADC_OVERSAMPLE * 2];    // Double buffer that DMA just used
int16_t * valid_data_buffer;      // Swapped by interrupt handler to achieve double buffering
uint32_t ekf_too_slow = 0;
uint32_t total_conversion_blocks = 0;
/**
 * @}
 */


/**
* @brief AHRS Main function
*/
int main()
{
  /* Brings up System using CMSIS functions, enables the LEDs. */
  PIOS_SYS_Init();
  
  /* Delay system */
  PIOS_DELAY_Init();
  
  /* Communication system */
  PIOS_COM_Init();
  
  /* ADC system */
  AHRS_ADC_Config(EKF_RATE, ADC_OVERSAMPLE);
  
  /* Magnetic sensor system */
  PIOS_I2C_Init();
  PIOS_HMC5843_Init();
  
  /* Setup the Accelerometer FS (Full-Scale) GPIO */
  PIOS_GPIO_Enable(0);
  SET_ACCEL_2G;
  
  /* Configure the HMC5843 Sensor */
  PIOS_HMC5843_ConfigTypeDef HMC5843_InitStructure;
  HMC5843_InitStructure.M_ODR = PIOS_HMC5843_ODR_10;
  HMC5843_InitStructure.Meas_Conf = PIOS_HMC5843_MEASCONF_NORMAL;
  HMC5843_InitStructure.Gain = PIOS_HMC5843_GAIN_2;
  HMC5843_InitStructure.Mode = PIOS_HMC5843_MODE_CONTINUOUS;
  PIOS_HMC5843_Config(&HMC5843_InitStructure);
  
  /* SPI link to master */
  PIOS_SPI_Init();
  
  lfsm_init();
  
  ahrs_state = AHRS_IDLE;;
  /* Use simple averaging filter for now */
  for (int i = 0; i < ADC_OVERSAMPLE; i++)
    fir_coeffs[i] = 1;
  fir_coeffs[ADC_OVERSAMPLE] = ADC_OVERSAMPLE;
  
  // Main loop
  while (1) {
    uint8_t loop_ctr;

    // Alive signal
    if (loop_ctr++ > 100) {
      PIOS_LED_Toggle(LED1);
      loop_ctr = 0;
    }
    
    // Get 3 ID bytes
    strcpy ((char *)mag_data.id, "ZZZ");
    PIOS_HMC5843_ReadID(mag_data.id);
    
    // Get magnetic readings
    PIOS_HMC5843_ReadMag(mag_data.raw.axis);
    
    // Delay for valid data
    while( ahrs_state != AHRS_DATA_READY );
    ahrs_state = AHRS_PROCESSING;

    downsample_data();
    
    // Hacky - grab one sample from buffer to populate this.  Need to send back
    // all raw data if it's happening
    accel_data.raw.x = valid_data_buffer[0];
    accel_data.raw.y = valid_data_buffer[2];
    accel_data.raw.z = valid_data_buffer[4];
    
    gyro_data.raw.x = valid_data_buffer[1];
    gyro_data.raw.y = valid_data_buffer[3];
    gyro_data.raw.z = valid_data_buffer[5];
    
    gyro_data.temp.xy = valid_data_buffer[6];
    gyro_data.temp.z = valid_data_buffer[7];    
    
    ahrs_state = AHRS_IDLE;
    
    /* Simulate a rotating airframe */
    attitude_data.quaternion.q1 += .001;
    attitude_data.quaternion.q2 += .002;
    attitude_data.quaternion.q3 += .003;
    attitude_data.quaternion.q4 += 1;

    attitude_data.euler.roll  += .004;
    if (attitude_data.euler.roll > 360.0) attitude_data.euler.roll -= 360.0;
    attitude_data.euler.pitch += .005;
    if (attitude_data.euler.pitch > 360.0) attitude_data.euler.pitch -= 360.0;
    attitude_data.euler.yaw   += .006;
    if (attitude_data.euler.yaw > 360.0) attitude_data.euler.yaw -= 360.0;
    
    process_spi_request();
    
    // Delay until next reading
    //PIOS_DELAY_WaitmS(50);
  }
  
  return 0;
}

/**
 * @brief Downsample the analog data
 * @return none
 *
 * Tried to make as much of the filtering fixed point when possible.  Need to account
 * for offset for each sample before the multiplication if filter not a boxcar.  Could
 * precompute fixed offset as sum[fir_coeffs[i]] * ACCEL_OFFSET.  Puts data into global
 * data structures @ref accel_data and @ref gyro_data.
 */
void downsample_data()
{
  int32_t accel_raw[3], gyro_raw[3];  
  uint16_t i;
  
  // Get the X data.  Fifth byte in.  Convert to m/s
  accel_raw[0] = 0;  
  for( i = 0; i < ADC_OVERSAMPLE; i++ )      
    accel_raw[0] = accel_raw[0] + ( valid_data_buffer[0 + (i-1) * ADC_CONTINUOUS_CHANNELS] + ACCEL_OFFSET ) * fir_coeffs[i];
  accel_data.filtered.x = (float) accel_raw[0] / (float) fir_coeffs[ADC_OVERSAMPLE] * ACCEL_SCALE;

  // Get the Y data.  Third byte in.  Convert to m/s
  accel_raw[1] = 0;  
  for( i = 0; i < ADC_OVERSAMPLE; i++ )      
    accel_raw[1] = accel_raw[1] + ( valid_data_buffer[2 + (i-1) * ADC_CONTINUOUS_CHANNELS] + ACCEL_OFFSET ) * fir_coeffs[i];
  accel_data.filtered.y = (float) accel_raw[1] / (float) fir_coeffs[ADC_OVERSAMPLE]  * ACCEL_SCALE;
  
  // Get the Z data.  Third byte in.  Convert to m/s
  accel_raw[2] = 0;  
  for( i = 0; i < ADC_OVERSAMPLE; i++ )      
    accel_raw[2] = accel_raw[2] + ( valid_data_buffer[4 + (i-1) * ADC_CONTINUOUS_CHANNELS] + ACCEL_OFFSET ) * fir_coeffs[i];
  accel_data.filtered.z = (float) accel_raw[2] / (float) fir_coeffs[ADC_OVERSAMPLE]  * ACCEL_SCALE;
  
  // Get the X gyro data.  Seventh byte in.  Convert to deg/s.
  gyro_raw[0] = 0;
  for( i = 0; i < ADC_OVERSAMPLE; i++ )
    gyro_raw[0] += gyro_raw[0] + ( valid_data_buffer[1 + (i-1) * ADC_CONTINUOUS_CHANNELS] + GYRO_OFFSET ) * fir_coeffs[i];
  gyro_data.filtered.x  = (float) gyro_raw[0] / (float) fir_coeffs[ADC_OVERSAMPLE] * GYRO_SCALE;
  
  // Get the Y gyro data.  Second byte in.  Convert to deg/s.
  gyro_raw[1] = 0;
  for( i = 0; i < ADC_OVERSAMPLE; i++ )
    gyro_raw[1] += gyro_raw[1] + ( valid_data_buffer[3 + (i-1) * ADC_CONTINUOUS_CHANNELS] + GYRO_OFFSET ) * fir_coeffs[i];
  gyro_data.filtered.y = (float) gyro_raw[1] / (float) fir_coeffs[ADC_OVERSAMPLE] * GYRO_SCALE;
  
  // Get the Z gyro data.  Fifth byte in.  Convert to deg/s.
  gyro_raw[2] = 0;
  for( i = 0; i < ADC_OVERSAMPLE; i++ )
    gyro_raw[2] += gyro_raw[2] + ( valid_data_buffer[5 + (i-1) * ADC_CONTINUOUS_CHANNELS] + GYRO_OFFSET ) * fir_coeffs[i];
  gyro_data.filtered.z = (float) gyro_raw[2] / (float) fir_coeffs[ADC_OVERSAMPLE] * GYRO_SCALE;
}


void dump_spi_message(uint8_t port, const char * prefix, uint8_t * data, uint32_t len)
{




}


static struct opahrs_msg_v1   link_tx_v1;
static struct opahrs_msg_v1   link_rx_v1;
static struct opahrs_msg_v1   user_rx_v1;
static struct opahrs_msg_v1   user_tx_v1;

void process_spi_request(void)
{
  bool msg_to_process = FALSE;

  PIOS_IRQ_Disable();
  /* Figure out if we're in an interesting stable state */
  switch (lfsm_get_state()) {
  case LFSM_STATE_USER_BUSY:
    msg_to_process = TRUE;
    break;
  case LFSM_STATE_INACTIVE:
    /* Queue up a receive buffer */
    lfsm_user_set_rx_v1 (&user_rx_v1);
    lfsm_user_done ();
    break;
  case LFSM_STATE_STOPPED:
    /* Get things going */
    lfsm_set_link_proto_v1 (&link_tx_v1, &link_rx_v1);
    break;
  default:
    /* Not a stable state */
    break;
  }
  PIOS_IRQ_Enable();

  if (!msg_to_process) {
    /* Nothing to do */
    //PIOS_COM_SendFormattedString(PIOS_COM_AUX, ".");
    return;
  }

  if (user_rx_v1.tail.magic != OPAHRS_MSG_MAGIC_TAIL) {
    PIOS_COM_SendFormattedString(PIOS_COM_AUX, "x");
  }

  /* We've got a message to process */
  //dump_spi_message(PIOS_COM_AUX, "+", (uint8_t *)&user_rx_v1, sizeof(user_rx_v1));

  switch (user_rx_v1.payload.user.t) {
  case OPAHRS_MSG_V1_REQ_SYNC:
    opahrs_msg_v1_init_user_tx (&user_tx_v1, OPAHRS_MSG_V1_RSP_SYNC);
    user_tx_v1.payload.user.v.rsp.sync.i_am_a_bootloader = FALSE;
    user_tx_v1.payload.user.v.rsp.sync.hw_version = 1;
    user_tx_v1.payload.user.v.rsp.sync.bl_version = 2;
    user_tx_v1.payload.user.v.rsp.sync.fw_version = 3;
    user_tx_v1.payload.user.v.rsp.sync.cookie     = user_rx_v1.payload.user.v.req.sync.cookie;
    dump_spi_message(PIOS_COM_AUX, "S", (uint8_t *)&user_tx_v1, sizeof(user_tx_v1));
    lfsm_user_set_tx_v1 (&user_tx_v1);
    break;
  case OPAHRS_MSG_V1_REQ_RESET:
    PIOS_DELAY_WaitmS(user_rx_v1.payload.user.v.req.reset.reset_delay_in_ms);
    PIOS_SYS_Reset();
    break;
  case OPAHRS_MSG_V1_REQ_SERIAL:
    opahrs_msg_v1_init_user_tx (&user_tx_v1, OPAHRS_MSG_V1_RSP_SERIAL);
    PIOS_SYS_SerialNumberGet((char *)&(user_tx_v1.payload.user.v.rsp.serial.serial_bcd));
    dump_spi_message(PIOS_COM_AUX, "I", (uint8_t *)&user_tx_v1, sizeof(user_tx_v1));
    lfsm_user_set_tx_v1 (&user_tx_v1);
    break;
  case OPAHRS_MSG_V1_REQ_ALTITUDE:
    opahrs_msg_v1_init_user_tx (&user_tx_v1, OPAHRS_MSG_V1_RSP_ALTITUDE);
    altitude_data.altitude    = user_rx_v1.payload.user.v.req.altitude.altitude;
    altitude_data.pressure    = user_rx_v1.payload.user.v.req.altitude.pressure;
    altitude_data.temperature = user_rx_v1.payload.user.v.req.altitude.temperature;
    dump_spi_message(PIOS_COM_AUX, "V", (uint8_t *)&user_rx_v1, sizeof(user_rx_v1));
    lfsm_user_set_tx_v1 (&user_tx_v1);
    break;
  case OPAHRS_MSG_V1_REQ_ATTITUDERAW:
    opahrs_msg_v1_init_user_tx (&user_tx_v1, OPAHRS_MSG_V1_RSP_ATTITUDERAW);
    user_tx_v1.payload.user.v.rsp.attituderaw.mags.x        = mag_data.raw.axis[0];
    user_tx_v1.payload.user.v.rsp.attituderaw.mags.y        = mag_data.raw.axis[1];
    user_tx_v1.payload.user.v.rsp.attituderaw.mags.z        = mag_data.raw.axis[2];

    user_tx_v1.payload.user.v.rsp.attituderaw.gyros.x       = gyro_data.raw.x;
    user_tx_v1.payload.user.v.rsp.attituderaw.gyros.y       = gyro_data.raw.y;
    user_tx_v1.payload.user.v.rsp.attituderaw.gyros.z       = gyro_data.raw.z;
    user_tx_v1.payload.user.v.rsp.attituderaw.gyros.xy_temp = gyro_data.temp.xy;
    user_tx_v1.payload.user.v.rsp.attituderaw.gyros.z_temp  = gyro_data.temp.z;

    user_tx_v1.payload.user.v.rsp.attituderaw.accels.x      = accel_data.raw.x;
    user_tx_v1.payload.user.v.rsp.attituderaw.accels.y      = accel_data.raw.y;
    user_tx_v1.payload.user.v.rsp.attituderaw.accels.z      = accel_data.raw.z;

    dump_spi_message(PIOS_COM_AUX, "R", (uint8_t *)&user_tx_v1, sizeof(user_tx_v1));
    lfsm_user_set_tx_v1 (&user_tx_v1);
    break;
  case OPAHRS_MSG_V1_REQ_ATTITUDE:
    opahrs_msg_v1_init_user_tx (&user_tx_v1, OPAHRS_MSG_V1_RSP_ATTITUDE);
    user_tx_v1.payload.user.v.rsp.attitude.quaternion.q1 = attitude_data.quaternion.q1;
    user_tx_v1.payload.user.v.rsp.attitude.quaternion.q2 = attitude_data.quaternion.q2;
    user_tx_v1.payload.user.v.rsp.attitude.quaternion.q3 = attitude_data.quaternion.q3;
    user_tx_v1.payload.user.v.rsp.attitude.quaternion.q4 = attitude_data.quaternion.q4;
    user_tx_v1.payload.user.v.rsp.attitude.euler.roll    = attitude_data.euler.roll;
    user_tx_v1.payload.user.v.rsp.attitude.euler.pitch   = attitude_data.euler.pitch;
    user_tx_v1.payload.user.v.rsp.attitude.euler.yaw     = attitude_data.euler.yaw;
    dump_spi_message(PIOS_COM_AUX, "A", (uint8_t *)&user_tx_v1, sizeof(user_tx_v1));
#if 1
    /* DEBUG: Overload q4 as a cycle counter since last read. */
    attitude_data.quaternion.q4 = 0;
#endif
    lfsm_user_set_tx_v1 (&user_tx_v1);
    break;
  default:
    break;
  }

  /* Finished processing the received message, requeue it */
  memset(&user_rx_v1, 0xAA, sizeof(user_rx_v1));
  lfsm_user_set_rx_v1 (&user_rx_v1);
  lfsm_user_done ();
}

/**
 * ADC Configuration local variabels 
 */
/* Local Variables */
static GPIO_TypeDef* ADC_GPIO_PORT[PIOS_ADC_NUM_PINS] = PIOS_ADC_PORTS;
static const uint32_t ADC_GPIO_PIN[PIOS_ADC_NUM_PINS] = PIOS_ADC_PINS;
static const uint32_t ADC_CHANNEL[PIOS_ADC_NUM_PINS] = PIOS_ADC_CHANNELS;

static ADC_TypeDef* ADC_MAPPING[PIOS_ADC_NUM_PINS] = PIOS_ADC_MAPPING;
static const uint32_t ADC_CHANNEL_MAPPING[PIOS_ADC_NUM_PINS] = PIOS_ADC_CHANNEL_MAPPING;


/**
 * Initialise the ADC Peripheral
 * @params ekf_rate
 */
void AHRS_ADC_Config(int32_t ekf_rate, int32_t adc_oversample)
{
  
	int32_t i;
  
	/* Setup analog pins */
	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_StructInit(&GPIO_InitStructure);
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
	GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AIN;
  
	/* Enable each ADC pin in the array */
	for(i = 0; i < PIOS_ADC_NUM_PINS; i++) {
		GPIO_InitStructure.GPIO_Pin = ADC_GPIO_PIN[i];
		GPIO_Init(ADC_GPIO_PORT[i], &GPIO_InitStructure);
	}
  
	/* Enable ADC clocks */
	PIOS_ADC_CLOCK_FUNCTION;
  
	/* Map channels to conversion slots depending on the channel selection mask */
	for(i = 0; i < PIOS_ADC_NUM_PINS; i++) {
		ADC_RegularChannelConfig(ADC_MAPPING[i], ADC_CHANNEL[i], ADC_CHANNEL_MAPPING[i], PIOS_ADC_SAMPLE_TIME);
	}
  
#if (PIOS_ADC_USE_TEMP_SENSOR)
	ADC_TempSensorVrefintCmd(ENABLE);
	ADC_RegularChannelConfig(PIOS_ADC_TEMP_SENSOR_ADC, ADC_Channel_14, PIOS_ADC_TEMP_SENSOR_ADC_CHANNEL, PIOS_ADC_SAMPLE_TIME);
#endif
  
  // TODO: update ADC to continuous sampling, configure the sampling rate
	/* Configure ADCs */
	ADC_InitTypeDef ADC_InitStructure;
	ADC_StructInit(&ADC_InitStructure);
	ADC_InitStructure.ADC_Mode = ADC_Mode_RegSimult;
	ADC_InitStructure.ADC_ScanConvMode = ENABLE;
	ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
	ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
	ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
	ADC_InitStructure.ADC_NbrOfChannel = 4; //((PIOS_ADC_NUM_CHANNELS + 1) >> 1);
	ADC_Init(ADC1, &ADC_InitStructure);
  
#if (PIOS_ADC_USE_ADC2)
	ADC_Init(ADC2, &ADC_InitStructure);
  
	/* Enable ADC2 external trigger conversion (to synch with ADC1) */
	ADC_ExternalTrigConvCmd(ADC2, ENABLE);
#endif
  
	//RCC_ADCCLKConfig(PIOS_ADC_ADCCLK);
  
	/* Enable ADC1->DMA request */
	ADC_DMACmd(ADC1, ENABLE);
  
	/* ADC1 calibration */
	ADC_Cmd(ADC1, ENABLE);
	ADC_ResetCalibration(ADC1);
	while(ADC_GetResetCalibrationStatus(ADC1));
	ADC_StartCalibration(ADC1);
	while(ADC_GetCalibrationStatus(ADC1));
  
#if (PIOS_ADC_USE_ADC2)
	/* ADC2 calibration */
	ADC_Cmd(ADC2, ENABLE);
	ADC_ResetCalibration(ADC2);
	while(ADC_GetResetCalibrationStatus(ADC2));
	ADC_StartCalibration(ADC2);
	while(ADC_GetCalibrationStatus(ADC2));
#endif
  
	/* Enable DMA1 clock */
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
  
	/* Configure DMA1 channel 1 to fetch data from ADC result register */
	DMA_InitTypeDef DMA_InitStructure;
	DMA_StructInit(&DMA_InitStructure);
	DMA_DeInit(DMA1_Channel1);
	DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
	DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&raw_data_buffer[0];
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
  /* We are double buffering half words from the ADC.  Make buffer appropriately sized */
	DMA_InitStructure.DMA_BufferSize = (ADC_CONTINUOUS_CHANNELS * ADC_OVERSAMPLE * 2) >> 1; 
	DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
	DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  /* Note: We read ADC1 and ADC2 in parallel making a word read, also hence the half buffer size */
	DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
	DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
	DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
	DMA_InitStructure.DMA_Priority = DMA_Priority_High;
	DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
	DMA_Init(DMA1_Channel1, &DMA_InitStructure);
	DMA_Cmd(DMA1_Channel1, ENABLE);
  
	/* Trigger interrupt when for half conversions too to indicate double buffer */
	DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);
	DMA_ITConfig(DMA1_Channel1, DMA_IT_HT, ENABLE);
  
	/* Configure and enable DMA interrupt */
	NVIC_InitTypeDef NVIC_InitStructure;
	NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel1_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = PIOS_ADC_IRQ_PRIO;
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);
  
	/* Finally start initial conversion */
	ADC_SoftwareStartConvCmd(ADC1, ENABLE);
}

void AHRS_ADC_DMA_Handler(void) 
{
  if ( ahrs_state == AHRS_IDLE ) 
  {
    // Ideally this would have a mutex, but I think we can avoid it (and don't have RTOS features)
    
    if( DMA_GetFlagStatus( DMA1_IT_TC1 ) ) // whole double buffer filled
      valid_data_buffer = &raw_data_buffer[ ADC_CONTINUOUS_CHANNELS * ADC_OVERSAMPLE ];
    else if ( DMA_GetFlagStatus(DMA1_IT_HT1) )
      valid_data_buffer = &raw_data_buffer[0];
    else {
      // lets cause a seg fault and catch whatever is going on
      valid_data_buffer = 0;
    }
    
    ahrs_state = AHRS_DATA_READY;
  }
  else {
    // Track how many times an interrupt occurred before EKF finished processing
    ekf_too_slow++;
  }
  
  total_conversion_blocks++;
  
  // Clear all interrupt from DMA 1 - regardless if buffer swapped
  DMA_ClearFlag( DMA1_IT_GL1 );
  
}