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Paul Thomase0c70b82010-05-24 14:33:38 -07001/*
2 * ads7871 - driver for TI ADS7871 A/D converter
3 *
4 * Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
5 *
6 * This program is distributed in the hope that it will be useful,
7 * but WITHOUT ANY WARRANTY; without even the implied warranty of
8 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
9 * GNU General Public License for more details.
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 or
13 * later as publishhed by the Free Software Foundation.
14 *
15 * You need to have something like this in struct spi_board_info
16 * {
17 * .modalias = "ads7871",
18 * .max_speed_hz = 2*1000*1000,
19 * .chip_select = 0,
20 * .bus_num = 1,
21 * },
22 */
23
24/*From figure 18 in the datasheet*/
25/*Register addresses*/
26#define REG_LS_BYTE 0 /*A/D Output Data, LS Byte*/
27#define REG_MS_BYTE 1 /*A/D Output Data, MS Byte*/
28#define REG_PGA_VALID 2 /*PGA Valid Register*/
29#define REG_AD_CONTROL 3 /*A/D Control Register*/
30#define REG_GAIN_MUX 4 /*Gain/Mux Register*/
31#define REG_IO_STATE 5 /*Digital I/O State Register*/
32#define REG_IO_CONTROL 6 /*Digital I/O Control Register*/
33#define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
34#define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
35#define REG_ID 31 /*ID Register*/
36
37/*From figure 17 in the datasheet
38* These bits get ORed with the address to form
39* the instruction byte */
40/*Instruction Bit masks*/
41#define INST_MODE_bm (1<<7)
42#define INST_READ_bm (1<<6)
43#define INST_16BIT_bm (1<<5)
44
45/*From figure 18 in the datasheet*/
46/*bit masks for Rev/Oscillator Control Register*/
47#define MUX_CNV_bv 7
48#define MUX_CNV_bm (1<<MUX_CNV_bv)
49#define MUX_M3_bm (1<<3) /*M3 selects single ended*/
50#define MUX_G_bv 4 /*allows for reg = (gain << MUX_G_bv) | ...*/
51
52/*From figure 18 in the datasheet*/
53/*bit masks for Rev/Oscillator Control Register*/
54#define OSC_OSCR_bm (1<<5)
55#define OSC_OSCE_bm (1<<4)
56#define OSC_REFE_bm (1<<3)
57#define OSC_BUFE_bm (1<<2)
58#define OSC_R2V_bm (1<<1)
59#define OSC_RBG_bm (1<<0)
60
61#include <linux/module.h>
62#include <linux/init.h>
63#include <linux/spi/spi.h>
64#include <linux/hwmon.h>
65#include <linux/hwmon-sysfs.h>
66#include <linux/err.h>
67#include <linux/mutex.h>
68#include <linux/delay.h>
69
70#define DEVICE_NAME "ads7871"
71
72struct ads7871_data {
73 struct device *hwmon_dev;
74 struct mutex update_lock;
75};
76
77static int ads7871_read_reg8(struct spi_device *spi, int reg)
78{
79 int ret;
80 reg = reg | INST_READ_bm;
81 ret = spi_w8r8(spi, reg);
82 return ret;
83}
84
85static int ads7871_read_reg16(struct spi_device *spi, int reg)
86{
87 int ret;
88 reg = reg | INST_READ_bm | INST_16BIT_bm;
89 ret = spi_w8r16(spi, reg);
90 return ret;
91}
92
93static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
94{
95 u8 tmp[2] = {reg, val};
96 return spi_write(spi, tmp, sizeof(tmp));
97}
98
99static ssize_t show_voltage(struct device *dev,
100 struct device_attribute *da, char *buf)
101{
102 struct spi_device *spi = to_spi_device(dev);
103 struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
104 int ret, val, i = 0;
105 uint8_t channel, mux_cnv;
106
107 channel = attr->index;
108 /*TODO: add support for conversions
109 *other than single ended with a gain of 1*/
110 /*MUX_M3_bm forces single ended*/
111 /*This is also where the gain of the PGA would be set*/
112 ads7871_write_reg8(spi, REG_GAIN_MUX,
113 (MUX_CNV_bm | MUX_M3_bm | channel));
114
115 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
116 mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
117 /*on 400MHz arm9 platform the conversion
118 *is already done when we do this test*/
119 while ((i < 2) && mux_cnv) {
120 i++;
121 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
122 mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
123 msleep_interruptible(1);
124 }
125
126 if (mux_cnv == 0) {
127 val = ads7871_read_reg16(spi, REG_LS_BYTE);
128 /*result in volts*10000 = (val/8192)*2.5*10000*/
129 val = ((val>>2) * 25000) / 8192;
130 return sprintf(buf, "%d\n", val);
131 } else {
132 return -1;
133 }
134}
135
136static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
137static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
138static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
139static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
140static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
141static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
142static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
143static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
144
145static struct attribute *ads7871_attributes[] = {
146 &sensor_dev_attr_in0_input.dev_attr.attr,
147 &sensor_dev_attr_in1_input.dev_attr.attr,
148 &sensor_dev_attr_in2_input.dev_attr.attr,
149 &sensor_dev_attr_in3_input.dev_attr.attr,
150 &sensor_dev_attr_in4_input.dev_attr.attr,
151 &sensor_dev_attr_in5_input.dev_attr.attr,
152 &sensor_dev_attr_in6_input.dev_attr.attr,
153 &sensor_dev_attr_in7_input.dev_attr.attr,
154 NULL
155};
156
157static const struct attribute_group ads7871_group = {
158 .attrs = ads7871_attributes,
159};
160
161static int __devinit ads7871_probe(struct spi_device *spi)
162{
Axel Linc12c5072010-08-25 15:42:10 +0200163 int ret, err;
Paul Thomase0c70b82010-05-24 14:33:38 -0700164 uint8_t val;
165 struct ads7871_data *pdata;
166
167 dev_dbg(&spi->dev, "probe\n");
168
Paul Thomase0c70b82010-05-24 14:33:38 -0700169 /* Configure the SPI bus */
170 spi->mode = (SPI_MODE_0);
171 spi->bits_per_word = 8;
172 spi_setup(spi);
173
174 ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
175 ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
176
177 val = (OSC_OSCR_bm | OSC_OSCE_bm | OSC_REFE_bm | OSC_BUFE_bm);
178 ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
179 ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
180
181 dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
182 /*because there is no other error checking on an SPI bus
183 we need to make sure we really have a chip*/
184 if (val != ret) {
185 err = -ENODEV;
Axel Linc12c5072010-08-25 15:42:10 +0200186 goto exit;
187 }
188
189 pdata = kzalloc(sizeof(struct ads7871_data), GFP_KERNEL);
190 if (!pdata) {
191 err = -ENOMEM;
192 goto exit;
193 }
194
195 err = sysfs_create_group(&spi->dev.kobj, &ads7871_group);
196 if (err < 0)
197 goto error_free;
198
199 spi_set_drvdata(spi, pdata);
200
201 pdata->hwmon_dev = hwmon_device_register(&spi->dev);
202 if (IS_ERR(pdata->hwmon_dev)) {
203 err = PTR_ERR(pdata->hwmon_dev);
Paul Thomase0c70b82010-05-24 14:33:38 -0700204 goto error_remove;
205 }
206
207 return 0;
208
209error_remove:
210 sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
211error_free:
212 kfree(pdata);
213exit:
214 return err;
215}
216
217static int __devexit ads7871_remove(struct spi_device *spi)
218{
219 struct ads7871_data *pdata = spi_get_drvdata(spi);
220
221 hwmon_device_unregister(pdata->hwmon_dev);
222 sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
223 kfree(pdata);
224 return 0;
225}
226
227static struct spi_driver ads7871_driver = {
228 .driver = {
229 .name = DEVICE_NAME,
Paul Thomase0c70b82010-05-24 14:33:38 -0700230 .owner = THIS_MODULE,
231 },
232
233 .probe = ads7871_probe,
234 .remove = __devexit_p(ads7871_remove),
235};
236
237static int __init ads7871_init(void)
238{
239 return spi_register_driver(&ads7871_driver);
240}
241
242static void __exit ads7871_exit(void)
243{
244 spi_unregister_driver(&ads7871_driver);
245}
246
247module_init(ads7871_init);
248module_exit(ads7871_exit);
249
250MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
251MODULE_DESCRIPTION("TI ADS7871 A/D driver");
252MODULE_LICENSE("GPL");