microstrain_imu.c File Reference

Control code for the Microstrain IMU on the UI board. More...

Go to the source code of this file.

Functions
float	msimu_get_data_float (MSIMU_DATA index)
	Returns data from the IMU as a float.
int	msimu_get_data_int (MSIMU_DATA index)
	Returns data from the IMU as an int.
int	msimu_get_length (MSIMU_COMMAND command)
	Returns the length of a return packet associated with a given command.
void	msimu_init (MSIMU_COMMAND command)
	Initializes the microstrin IMU module.
void	msimu_isr (void)
	The interrupt service routine for communicating with the IMU over UART.
void	msimu_parse_buffer (void)
	Parses the UART buffer to check for a new packet, saving the data if there has been a new packet.
void	msimu_send_all (unsigned char *bytes, unsigned int length)
	Sends bytes to the IMU over UART.
void	msimu_set_continuous (MSIMU_COMMAND command)
	Starts the IMU in continuous mode with the given command.
void	msimu_update (void)
	Updates the IMU module.
Variables
MSIMU_COMMAND	msimu_continuous_command
unsigned long	msimu_data_buffer [20]
unsigned char	msimu_rb_index1 = 0
unsigned char	msimu_rb_index2 = 0
unsigned char	msimu_read_buffer [128]
unsigned char	msimu_tb_index1 = 0
unsigned char	msimu_tb_index2 = 0
unsigned char	msimu_trans_buffer [128]

---

Detailed Description

Control code for the Microstrain IMU on the UI board.

Example hardware setup for communicating with IMU over UART:

  // *******************************************************************************
  // Initialize Microstrain IMU over UART1
  // *******************************************************************************
  U1LCR=0x83;  //Step 1: DLAB=1, enable baud rate adjustments
  //Set to 8 data bits, 1 stop bit, no parity
  //Step 2: Set baud rate divisor and fractional baud rate divisors
  U1DLL=25;   //Baud rate divisor for 115200 kbaud, with (1+0.3) fractional divider 
  U1DLM=0;    //and peripheral clock = 60MHz.
  U1FDR = 3;    // DIVADDVAL = 3
  U1FDR |= 10<<4; // MULTVAL = 10
  //U1FCR = 0x81;     // Enable receive and transmit FIFO; interrupt on receive at 8 bytes.
  U1FCR = 0x1;    // Enable FIFO
  U1FCR = 0x87;   //Clear FIFOs and set to generate interrupt when RX FIFO reaches 8 bytes.
  U1MCR = 0;      // Loopback mode, CTS and RTS flow control disabled.
  U1ACR = 0;      // Autobaud disabled
  U1TER = 0x80;     // Transmit enabled
  U1LCR &= ~(1<<7); // Step 3: DLAB=0, disable baud rate adjustments
  PINSEL0 |= 1<<16;    // UART1 TXD active on MCU pin P0[8]
  PINSEL0 &= ~(1<<17); //
  PINSEL0 |= 1<<18;    // UART1 RXD active on MCU pin P0[9]
  PINSEL0 &= ~(1<<19); //
  U1IER = (1<<0); // enable RBR interrupts
  U1ACR = (1<<8) | (1<<9); //clear the corresponding interrupt in the U1IIR

Author:

Nicolas Williamson

Jason Cortell

Date:

December 2009

Definition in file microstrain_imu.c.

---

Function Documentation

float msimu_get_data_float

(

MSIMU_DATA

index

)

Returns data from the IMU as a float.

Parameters:

index

The index of the data from the packet.

See also:

MSIMU_DATA

Returns:

The requested data interpreted as a float.

Note:

This function only interprets the bits coming in over the UART as a floating point number, it does NOT convert from an integer (1) to float (1.0).

Definition at line 207 of file microstrain_imu.c.

                                            {
  void *vpointer;
  float *fpointer;
  float data;
  vpointer = msimu_data_buffer + index;
  fpointer = vpointer; 
  data = *fpointer;
  return data;
}

int msimu_get_data_int

(

MSIMU_DATA

index

)

Returns data from the IMU as an int.

Parameters:

index

The index of the data from the packet.

See also:

MSIMU_DATA

Returns:

The requested data interpreted as an int.

Note:

This function only interprets the bits coming in over the UART as an integer, it does NOT convert from an float (1.4) to int (1).

Definition at line 224 of file microstrain_imu.c.

                                        {
  return (int)msimu_data_buffer[index];
}

int msimu_get_length

(

MSIMU_COMMAND

command

)

Returns the length of a return packet associated with a given command.

Note:

Not all commands have been added. If you do not see yours listed, add it to the switch statement.

Parameters:

command

The command to get the return packet length of.

Returns:

Length of the expected return packet, or 31 if command is unknown.

Definition at line 75 of file microstrain_imu.c.

Referenced by msimu_parse_buffer().

                                           {
  int length = 0;
  switch (command){
    case MSIMU_RAW_ACCEL_ANG_RATE: length = 31; break;
    case MSIMU_EULER_ANGS_ANG_RATE: length = 31; break;
    default: length = 31;
  }
  return length;
}

void msimu_init

(

MSIMU_COMMAND

command

)

Initializes the microstrin IMU module.

Parameters:

command

The data that the IMU will continuously calculate and send to the board over UART.

Definition at line 63 of file microstrain_imu.c.

References msimu_set_continuous().

{
  msimu_set_continuous(command);
}

void msimu_isr

(

void

)

The interrupt service routine for communicating with the IMU over UART.

Stores incoming data into buffers.

Definition at line 89 of file microstrain_imu.c.

References error_occurred().

{ 
  unsigned long int interrupt_id, line_status;
  unsigned short int i;

  interrupt_id = U1IIR;
  //test_counter++;
  
  switch (interrupt_id & 0xE) //Look at bits 1 - 3 of U1IIR
  {
   case 4:  //receive data available (>=8 bytes in hardware receive FIFO, as set in U1FCR)
     for (i=0;i<8;i++)
     {
       line_status = U1LSR;
       msimu_read_buffer[msimu_rb_index1] = U1RBR;  //Put new data in next buffer location
       msimu_rb_index1 = (++msimu_rb_index1 & 127);   //Increment index; roll over to 0 after reaching 127  

       if (msimu_rb_index1 == msimu_rb_index2)      //software receive software overflow
       {
         msimu_rb_index1 = (--msimu_rb_index1 & 127); //overwrite most recent byte
         error_occurred(ERROR_MSIMU_RX_OF);
       }  
     }
   break;

   case 12: //character time-out - at least one left-over byte in hardware receive FIFO
     line_status = U1LSR;
     msimu_read_buffer[msimu_rb_index1] = U1RBR;  //Put new data in next buffer location
     msimu_rb_index1 = (++msimu_rb_index1 & 127);   //Increment index; roll over to 0 after reaching 127  

     if (msimu_rb_index1 == msimu_rb_index2)    //software receive buffer overflow
     {
       msimu_rb_index1 = (--msimu_rb_index1 & 127);  //overwrite most recent byte
       error_occurred(ERROR_MSIMU_RX_OF);
     }  
   
   break;
   
   case 2:  //transmitter hardware FIFO empty
     for (i=0;i<16;i++)   //Move up to 16 bytes (FIFO capacity) to FIFO
     {
       if (msimu_tb_index1 != msimu_tb_index2)  //Transmit software FIFO not empty
       {
       U1THR = msimu_trans_buffer[msimu_tb_index2]; //Transmit oldest byte from software FIFO
       msimu_tb_index2 = ((++msimu_tb_index2) & 127);   //Increment Index2, roll over at 128
       }
       else
       {
       U1IER &= ~(1<<1);    //Disable tranmitter holding register empty interrupt, bit 1
       break;
       }
     }   
   break;
   
   case 6:  //receive line status interrupt
    line_status = U1LSR;
    switch(line_status & 30){
      case 1: //Overrun Error(OE)
        //mcu_led_red_blink(500);
        break;
      case 2: //Parity Error(PE)
        //mcu_led_green_blink(500);
        break;
      case 4: //Framing Error(FE)
        //mcu_led_red_blink(2000);
        break;
      case 8: //Break Interrupt(BI)
        //mcu_led_green_blink(2000);
        break;
    }
   break; 
       
  }      
  
  VICVectAddr = 0;    //Reset interrupt priorities
}  

void msimu_send_all	(	unsigned char *	bytes,
		unsigned int	length
	)

Sends bytes to the IMU over UART.

Parameters:

	bytes	An array of bytes to send.
	length	The length of the array of bytes.

Definition at line 183 of file microstrain_imu.c.

References error_occurred().

Referenced by msimu_set_continuous().

{
  unsigned int i;
  if ((length <= 16))   //length must be smaller than 16-byte FIFO and FIFO must be empty
  {                   
    if (U1LSR & (1<<5)){
      for (i=0;i<length;i++){
        U1THR = *(bytes + i);
      } 
    } else {
      error_occurred(ERROR_MSIMU_TX_FULL);
    }
  } else {
    error_occurred(ERROR_MSIMU_NUM_BYT);
  }
}

void msimu_set_continuous

(

MSIMU_COMMAND

command

)

Starts the IMU in continuous mode with the given command.

Parameters:

command

The command for the IMU to continuously compute.

Definition at line 170 of file microstrain_imu.c.

References msimu_send_all().

Referenced by msimu_init().

                                                {
  unsigned char c = command;
  unsigned char bytes[] = {0xC4,0xC1,0x29,0x00};
  bytes[3] = c;
  msimu_continuous_command = command;
  msimu_send_all(bytes, 4);
}

void msimu_update

(

void

)

Updates the IMU module.

Parses data from UART and check if there is a new packet. Call this from every row of the schedule.

Definition at line 232 of file microstrain_imu.c.

References msimu_parse_buffer().

{msimu_parse_buffer();}