modules/devices/encoders/encoders_spi/encoders_spi.c

   1 /*
   2  *  Copyright Droids Corporation (2009)
   3  *
   4  *  This program is free software; you can redistribute it and/or modify
   5  *  it under the terms of the GNU General Public License as published by
   6  *  the Free Software Foundation; either version 2 of the License, or
   7  *  (at your option) any later version.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU General Public License
  15  *  along with this program; if not, write to the Free Software
  16  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  *
  18  *  Revision : $Id: encoders_spi.c,v 1.1.2.3 2009-04-07 20:00:46 zer0 Exp $
  19  *
  20  *  Olivier MATZ <zer0@droids-corp.org>
  21  */
  22
  23 /* This modules handles encoders: values are read through a SPI
  24  * interface. Basically, frames are formatted with 4 words of 16 bits,
  25  * describing the values of the 4 encoders. */
  26
  27 #include <string.h>
  28
  29 #include <aversive.h>
  30 #include <aversive/parts.h>
  31
  32 #include <spi.h>
  33
  34 #include <encoders_spi.h>
  35 #include <encoders_spi_config.h>
  36
  37 static int32_t g_encoders_spi_values[ENCODERS_SPI_NUMBER];
  38 static int16_t g_encoders_spi_previous[ENCODERS_SPI_NUMBER];
  39
  40
  41 /* Initialisation of encoders, variables */
  42 void encoders_spi_init(void)
  43 {
  44         memset(g_encoders_spi_previous, 0, sizeof(g_encoders_spi_previous));
  45         spi_register_ss_line(&ENCODERS_SPI_SS_PORT, ENCODERS_SPI_SS_BIT);
  46         spi_init(SPI_MODE_MASTER, ENCODERS_SPI_FORMAT, ENCODERS_SPI_CLK_RATE);
  47         spi_set_data_order(ENCODERS_SPI_DATA_ORDER);
  48         encoders_spi_manage(NULL);
  49         memset(g_encoders_spi_values, 0, sizeof(g_encoders_spi_values));
  50 }
  51
  52
  53 /* Update encoders values */
  54 void encoders_spi_manage(__attribute__((unused)) void *dummy)
  55 {
  56         union {
  57                 struct {
  58                         uint8_t u8_lsb;
  59                         uint8_t u8_msb;
  60                 } s;
  61                 int16_t s16;
  62         } enc;
  63         uint8_t i;
  64         int16_t diff;
  65         uint8_t flags;
  66
  67         spi_slave_select(0);
  68         for (i=0; i<ENCODERS_SPI_NUMBER; i++) {
  69                 enc.s.u8_lsb = spi_receive_byte();
  70                 enc.s.u8_msb = spi_receive_byte();
  71                 diff = enc.s16 - g_encoders_spi_previous[i];
  72                 g_encoders_spi_previous[i] = enc.s16;
  73                 IRQ_LOCK(flags);
  74                 g_encoders_spi_values[i] += diff;
  75                 IRQ_UNLOCK(flags);
  76         }
  77         spi_slave_deselect(0);
  78 }
  79
  80
  81
  82 /* Extract encoder value */
  83 int32_t encoders_spi_get_value(void *encoder)
  84 {
  85         int32_t value;
  86         uint8_t flags;
  87
  88         IRQ_LOCK(flags);
  89         value = g_encoders_spi_values[(int)encoder];
  90         IRQ_UNLOCK(flags);
  91
  92         return value;
  93 }
  94
  95 /* Set an encoder value */
  96 void encoders_spi_set_value(void *encoder, int32_t val)
  97 {
  98         uint8_t flags;
  99
 100         IRQ_LOCK(flags);
 101         g_encoders_spi_values[(int)encoder] = val;
 102         IRQ_UNLOCK(flags);
 103 }