dev/i2c/i2c-ds1621.c

0001 /* Trivial i2c driver for the maxim DS1621 temperature sensor;
0002  * just implements reading constant conversions with 8-bit
0003  * resolution.
0004  * Demonstrates the implementation of a i2c high-level driver.
0005  */
0006
0007 /*
0008  * Authorship
0009  * ----------
0010  * This software was created by
0011  *     Till Straumann <strauman@slac.stanford.edu>, 2005,
0012  *     Stanford Linear Accelerator Center, Stanford University.
0013  *
0014  * Acknowledgement of sponsorship
0015  * ------------------------------
0016  * This software was produced by
0017  *     the Stanford Linear Accelerator Center, Stanford University,
0018  *     under Contract DE-AC03-76SFO0515 with the Department of Energy.
0019  *
0020  * Government disclaimer of liability
0021  * ----------------------------------
0022  * Neither the United States nor the United States Department of Energy,
0023  * nor any of their employees, makes any warranty, express or implied, or
0024  * assumes any legal liability or responsibility for the accuracy,
0025  * completeness, or usefulness of any data, apparatus, product, or process
0026  * disclosed, or represents that its use would not infringe privately owned
0027  * rights.
0028  *
0029  * Stanford disclaimer of liability
0030  * --------------------------------
0031  * Stanford University makes no representations or warranties, express or
0032  * implied, nor assumes any liability for the use of this software.
0033  *
0034  * Stanford disclaimer of copyright
0035  * --------------------------------
0036  * Stanford University, owner of the copyright, hereby disclaims its
0037  * copyright and all other rights in this software.  Hence, anyone may
0038  * freely use it for any purpose without restriction.
0039  *
0040  * Maintenance of notices
0041  * ----------------------
0042  * In the interest of clarity regarding the origin and status of this
0043  * SLAC software, this and all the preceding Stanford University notices
0044  * are to remain affixed to any copy or derivative of this software made
0045  * or distributed by the recipient and are to be affixed to any copy of
0046  * software made or distributed by the recipient that contains a copy or
0047  * derivative of this software.
0048  *
0049  * ------------------ SLAC Software Notices, Set 4 OTT.002a, 2004 FEB 03
0050  */
0051 #include <rtems.h>
0052 #include <rtems/libi2c.h>
0053
0054 #include <libchip/i2c-ds1621.h>
0055
0056 #include <rtems/libio.h>
0057
0058
0059 static rtems_status_code
0060 ds1621_init (rtems_device_major_number major, rtems_device_minor_number minor,
0061              void *arg)
0062 {
0063   int sc;
0064   unsigned char csr[2] = { DS1621_CMD_CSR_ACCESS, 0 }, cmd;
0065
0066   /* First start command acquires a lock for the bus */
0067
0068   /* Initialize; switch continuous conversion on */
0069   sc = rtems_libi2c_start_write_bytes (minor, csr, 1);
0070   if (sc < 0)
0071     return -sc;
0072
0073   sc = rtems_libi2c_start_read_bytes (minor, csr + 1, 1);
0074   if (sc < 0)
0075     return -sc;
0076
0077   csr[1] &= ~DS1621_CSR_1SHOT;
0078
0079   sc = rtems_libi2c_start_write_bytes (minor, csr, 2);
0080   if (sc < 0)
0081     return -sc;
0082
0083   /* Start conversion */
0084   cmd = DS1621_CMD_START_CONV;
0085
0086   sc = rtems_libi2c_start_write_bytes (minor, &cmd, 1);
0087   if (sc < 0)
0088     return -sc;
0089
0090   /* sending 'stop' relinquishes the bus mutex -- don't hold it
0091    * across system calls!
0092    */
0093   return rtems_libi2c_send_stop (minor);
0094 }
0095
0096 static rtems_status_code
0097 ds1621_read (rtems_device_major_number major, rtems_device_minor_number minor,
0098              void *arg)
0099 {
0100   int sc;
0101   rtems_libio_rw_args_t *rwargs = arg;
0102   unsigned char cmd = DS1621_CMD_READ_TEMP;
0103
0104   sc = rtems_libi2c_start_write_bytes (minor, &cmd, 1);
0105   if (sc < 0)
0106     return -sc;
0107   if (sc < 1)
0108     return RTEMS_IO_ERROR;
0109   sc = rtems_libi2c_start_read_bytes(minor, (unsigned char *)rwargs->buffer, 1);
0110   if (sc < 0) {
0111     rwargs->bytes_moved = 0;
0112     return -sc;
0113   }
0114   rwargs->bytes_moved = 1;
0115   return rtems_libi2c_send_stop (minor);
0116 }
0117
0118 static rtems_driver_address_table myops = {
0119   .initialization_entry = ds1621_init,
0120   .read_entry =           ds1621_read,
0121 };
0122
0123 static rtems_libi2c_drv_t my_drv_tbl = {
0124   .ops =                  &myops,
0125   .size =                 sizeof (my_drv_tbl),
0126 };
0127
0128 rtems_libi2c_drv_t *i2c_ds1621_driver_descriptor = &my_drv_tbl;