hcl_uart.c

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//==============================================================================
//
//  hcl_uart.c - Seiko Epson Hardware Control Library
//
//  This layer of indirection is added to allow the sample code to call generic
//  UART functions to work on multiple hardware platforms. This is the Linux
//  TERMIOS specific implementation.
//
//
//  THE SOFTWARE IS RELEASED INTO THE PUBLIC DOMAIN.
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  NONINFRINGEMENT, SECURITY, SATISFACTORY QUALITY, AND FITNESS FOR A
//  PARTICULAR PURPOSE. IN NO EVENT SHALL EPSON BE LIABLE FOR ANY LOSS, DAMAGE
//  OR CLAIM, ARISING FROM OR IN CONNECTION WITH THE SOFTWARE OR THE USE OF THE
//  SOFTWARE.
//
//==============================================================================
 
#include <assert.h>
#include <errno.h>  // Error number definitions
#include <fcntl.h>  // File control definitions
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>  // Needed for ioctl library functions
#include <termios.h>    // terminal io (serial port) interface
#include <unistd.h>
 
#include "hcl.h"
#include "hcl_uart.h"
#include "sensor_epsonCommon.h"
 
extern const char* IMUSERIAL;
static int fd_serial;
 
// Local function prototypes
int openComPort(const char* comPortPath, speed_t baudRate);
void closeComPort(void);
int deviceOk(void);
 
/*****************************************************************************
** Function name:       uartInit
** Description:         Initialize the COM port with the settings for
**                      communicating with the connected Epson IMU.
**                      Call this function instead of openComPort().
** Parameters:          Pointer to device name, baudrate
** Return value:        OK or NG
*****************************************************************************/
int uartInit(const char* comPortPath, int baudrate) {
  printf("Attempting to open port...%s", comPortPath);
 
  speed_t baudRate;
 
  switch (baudrate) {
    case BAUD_2000000:
      baudRate = B2000000;
      break;
    case BAUD_1500000:
      baudRate = B1500000;
      break;
    case BAUD_1000000:
      baudRate = B1000000;
      break;
    case BAUD_921600:
      baudRate = B921600;
      break;
    case BAUD_460800:
      baudRate = B460800;
      break;
    case BAUD_230400:
      baudRate = B230400;
      break;
    default:
      printf("Invalid baudrate\n");
      return NG;
  }
 
  if (!openComPort(comPortPath, baudRate)) {
    return NG;
  }
 
  if (!deviceOk()) {
    printf("Invalid device response\n");
    return NG;
  }
  return OK;
}
 
/*****************************************************************************
** Function name:       uartRelease
** Description:         Release the COM port (close) after a 100msec delay
**                      and closing the com port to the Epson IMU.
**                      Call this function instead of closeComPort().
** Parameters:          COM port handle
** Return value:        OK
*****************************************************************************/
int uartRelease(void) {
  seDelayMS(100);  // Provide 100msec delay for any pending transfer to complete
  closeComPort();
  return OK;
}
 
/*****************************************************************************
** Function name:       readComPort
** Description:         Read the specified number of bytes from the COM port
** Parameters:          COM port handle, pointer to output char array, # of
**                      bytes to read
** Return value:        # of bytes returned by COM port, or -1=NG
*****************************************************************************/
int readComPort(unsigned char* bytesToRead, int size) {
  return read(fd_serial, bytesToRead, size);
}
 
/*****************************************************************************
** Function name:       writeComPort
** Description:         Write specified number of bytes to the COM port
** Parameters:          COM port handle, pointer to input char array, # of bytes
**                      to send
** Return value:        # of bytes sent, or -1=NG
*****************************************************************************/
int writeComPort(unsigned char* bytesToWrite, int size) {
  return write(fd_serial, bytesToWrite, size);
}
 
/*****************************************************************************
** Function name:       numBytesReadComPort
** Description:         Returns number of bytes in COM port read buffer
**                      Purpose is to check if data is available
** Parameters:          COM port handle
** Return value:        # of bytes in the COM port receive buffer
*****************************************************************************/
int numBytesReadComPort(void) {
  int numBytes;
 
  ioctl(fd_serial, FIONREAD, &numBytes);
  return numBytes;
}
 
/*****************************************************************************
** Function name:       purgeComPort
** Description:         Clears the com port's read and write buffers
** Parameters:          COM port handle
** Return value:        OK or NG
*****************************************************************************/
int purgeComPort(void) {
  if (tcflush(fd_serial, TCIOFLUSH) == -1) {
    printf("flush failed\n");
    return NG;
  }
  return OK;
}
 
/*****************************************************************************
** Function name:       openComPort
** Description:         Com port is opened in raw mode and
**                      will timeout on reads after 2 second.
**                      This will return a NG if the port could not open or
**                      the port options could not be set.
**                      This is not intended to be called directly, but is
**                      called from uartInit()
** Parameters:          Pointer to device name, Baudrate
** Return value:        OK or NG
*****************************************************************************/
int openComPort(const char* comPortPath, speed_t baudRate) {
  // Read/Write, Not Controlling Terminal
  fd_serial = open(comPortPath, O_RDWR | O_NOCTTY);
 
  if (fd_serial < 0)  // Opening of port is NG
  {
    printf("...Unable to open com Port %s\n", comPortPath);
    return NG;
  }
 
  // Get the current options for the port...
  struct termios options;
  tcgetattr(fd_serial, &options);
 
  // Set the baud rate to 460800
  cfsetospeed(&options, baudRate);
  cfsetispeed(&options, baudRate);
 
  // From https://en.wikibooks.org/wiki/Serial_Programming/termios
  // Input flags - Turn off input processing
  // convert break to null byte, no CR to NL translation,
  // no NL to CR translation, don't mark parity errors or breaks
  // no input parity check, don't strip high bit off,
  // no XON/XOFF software flow control
  options.c_iflag &=
    ~(IGNBRK | BRKINT | ICRNL | INLCR | PARMRK | INPCK | ISTRIP | IXON);
 
  options.c_oflag = 0;  // raw output
 
  // No line processing
  // echo off, echo newline off, canonical mode off,
  // extended input processing off, signal chars off
 
  options.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);
 
  // Turn off character processing
  // clear current char size mask, no parity checking,
  // no output processing, force 8 bit input
 
  options.c_cflag &= ~(CSIZE | PARENB);
  options.c_cflag |= CS8;
 
  // From http://www.cmrr.umn.edu/~strupp/serial.html
  // Timeouts are ignored in canonical input mode or when the NDELAY option is
  // set on the file via open or fcntl. VMIN specifies the minimum number of
  // characters to read. 1) If VMIN is set to 0, then the VTIME value specifies
  // the time to wait for every characters to be read. The read call will return
  // even if less than specified from the read request. 2) If VMIN is non-zero,
  // VTIME specifies the time to wait for the first character. If first
  // character is received within the specified VTIME, then it won't return
  // until VMIN number of characters are received. So any read call can return
  // either 0 characters or N-specified characters, but nothing inbetween. It
  // will block forever if RX characters are not in multiples of VMIN. 3) VTIME
  // specifies the amount of time to wait for incoming characters in tenths of
  // seconds. If VTIME is set to 0 (the default), reads will block (wait)
  // indefinitely unless the NDELAY option is set on the port with open or fcntl
  // Setting VTIME = 0, makes UART reads blocking, try experimenting with value
  // to prevent hanging waiting for reads
 
  options.c_cc[VMIN] = 0;    // No min # of characters to read
  options.c_cc[VTIME] = 20;  // Timeout for 1st character is X*0.1secs = 2secs
 
  // Set local mode and enable the receiver
  options.c_cflag |= (CLOCAL | CREAD);
 
  // Change attributes when output has drained; also flush pending input.
  int status = tcsetattr(fd_serial, TCSAFLUSH, &options);
 
  if (status != 0)  // For error message
  {
    printf("Configuring comport failed\n");
    closeComPort();
    return NG;
  }
 
  // Purge serial port buffers
  purgeComPort();
 
  return OK;
}
 
/*****************************************************************************
** Function name:       closeComPort
** Description:         Closes a Com port (previously opened with OpenComPort)
**                      This is not intended to be called directly, but is
**                      called from uartRelease()
** Parameters:          COM port handle
** Return value:        None
*****************************************************************************/
void closeComPort(void) { close(fd_serial); }
 
/*****************************************************************************
** Function name:       deviceOk
** Description:         (Optional) Checks for Epson device.
**                      Attempts to recover if UART interface to device
**                      is inconsistent
** Parameters:          None
** Return value:        OK or NG
*****************************************************************************/
int deviceOk(void) {
  int retry_count = 5;
  unsigned char response[4] = {0};
  unsigned char SET_WIN_ID0[] = {0xFE, 0x00, 0x0D};
  unsigned char SET_CONFIG_MODE[] = {0x83, 0x02, 0x0D};
  unsigned char GET_ID[] = {0x4C, 0x00, 0x0D};
  unsigned char DELIMITER_[] = {0x0D};
  const unsigned short ID_VAL_ = 0x5345;
  unsigned short resp16;
 
  while (retry_count > 0) {
    int num_rcv_bytes;
    writeComPort(SET_WIN_ID0, 3);
    epsonStall();
 
    writeComPort(SET_CONFIG_MODE, 3);
    epsonStall();
 
    seDelayMS(100);  // delay for pending transfer to complete
    purgeComPort();
    num_rcv_bytes = numBytesReadComPort();
 
    // If receive buffer is empty, and ID register check is ok, then return OK
    if (num_rcv_bytes == 0) {
      writeComPort(GET_ID, 3);
      epsonStall();
 
      num_rcv_bytes = readComPort(&response[0], 4);
      if (num_rcv_bytes == 4) {
        resp16 = (unsigned short)response[1] << 8 | (unsigned short)response[2];
        if (resp16 == ID_VAL_) {
          return OK;
        }
      }
    }
    // If receive buffer is not empty or ID check fails,
    // send a DELIMITER byte and go thru loop again
    writeComPort(DELIMITER_, 1);
    retry_count--;
  }
  return NG;
}