1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
/* $Id$ */
/* Trivial i2c driver for the maxim DS1621 temperature sensor;
* just implements reading constant conversions with 8-bit
* resolution.
* Demonstrates the implementation of a i2c high-level driver.
*/
/* Author: Till Straumann, 2005 */
#include <rtems.h>
#include <rtems/libi2c.h>
#include <libchip/i2c-ds1621.h>
#include <rtems/libio.h>
static rtems_status_code
ds1621_init (rtems_device_major_number major, rtems_device_minor_number minor,
void *arg)
{
int sc;
unsigned char csr[2] = { DS1621_CMD_CSR_ACCESS, 0 }, cmd;
/* First start command acquires a lock for the bus */
/* Initialize; switch continuous conversion on */
sc = rtems_libi2c_start_write_bytes (minor, csr, 1);
if (sc < 0)
return -sc;
sc = rtems_libi2c_start_read_bytes (minor, csr + 1, 1);
if (sc < 0)
return -sc;
csr[1] &= ~DS1621_CSR_1SHOT;
sc = rtems_libi2c_start_write_bytes (minor, csr, 2);
if (sc < 0)
return -sc;
/* Start conversion */
cmd = DS1621_CMD_START_CONV;
sc = rtems_libi2c_start_write_bytes (minor, &cmd, 1);
if (sc < 0)
return -sc;
/* sending 'stop' relinquishes the bus mutex -- don't hold it
* across system calls!
*/
return rtems_libi2c_send_stop (minor);
}
static rtems_status_code
ds1621_read (rtems_device_major_number major, rtems_device_minor_number minor,
void *arg)
{
int sc;
rtems_libio_rw_args_t *rwargs = arg;
unsigned char cmd = DS1621_CMD_READ_TEMP;
sc = rtems_libi2c_start_write_bytes (minor, &cmd, 1);
if (sc < 0)
return -sc;
if (sc < 1)
return RTEMS_IO_ERROR;
sc = rtems_libi2c_start_read_bytes(minor, (unsigned char *)rwargs->buffer, 1);
if (sc < 0) {
rwargs->bytes_moved = 0;
return -sc;
}
rwargs->bytes_moved = 1;
return rtems_libi2c_send_stop (minor);
}
static rtems_driver_address_table myops = {
initialization_entry: ds1621_init,
read_entry: ds1621_read,
};
static rtems_libi2c_drv_t my_drv_tbl = {
ops: &myops,
size: sizeof (my_drv_tbl),
};
rtems_libi2c_drv_t *i2c_ds1621_driver_descriptor = &my_drv_tbl;
|
