1/*
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/*
38 * From figure 17 in the datasheet
39 * These bits get ORed with the address to form
40 * the instruction byte
41 */
42/*Instruction Bit masks*/
43#define INST_MODE_BM (1 << 7)
44#define INST_READ_BM (1 << 6)
45#define INST_16BIT_BM (1 << 5)
46
47/*From figure 18 in the datasheet*/
48/*bit masks for Rev/Oscillator Control Register*/
49#define MUX_CNV_BV 7
50#define MUX_CNV_BM (1 << MUX_CNV_BV)
51#define MUX_M3_BM (1 << 3) /*M3 selects single ended*/
52#define MUX_G_BV 4 /*allows for reg = (gain << MUX_G_BV) | ...*/
53
54/*From figure 18 in the datasheet*/
55/*bit masks for Rev/Oscillator Control Register*/
56#define OSC_OSCR_BM (1 << 5)
57#define OSC_OSCE_BM (1 << 4)
58#define OSC_REFE_BM (1 << 3)
59#define OSC_BUFE_BM (1 << 2)
60#define OSC_R2V_BM (1 << 1)
61#define OSC_RBG_BM (1 << 0)
62
63#include <linux/module.h>
64#include <linux/init.h>
65#include <linux/spi/spi.h>
66#include <linux/hwmon.h>
67#include <linux/hwmon-sysfs.h>
68#include <linux/err.h>
69#include <linux/delay.h>
70
71#define DEVICE_NAME "ads7871"
72
73struct ads7871_data {
74 struct spi_device *spi;
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 voltage_show(struct device *dev, struct device_attribute *da,
100 char *buf)
101{
102 struct ads7871_data *pdata = dev_get_drvdata(dev);
103 struct spi_device *spi = pdata->spi;
104 struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
105 int ret, val, i = 0;
106 uint8_t channel, mux_cnv;
107
108 channel = attr->index;
109 /*
110 * TODO: add support for conversions
111 * other than single ended with a gain of 1
112 */
113 /*MUX_M3_BM forces single ended*/
114 /*This is also where the gain of the PGA would be set*/
115 ads7871_write_reg8(spi, REG_GAIN_MUX,
116 (MUX_CNV_BM | MUX_M3_BM | channel));
117
118 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
119 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
120 /*
121 * on 400MHz arm9 platform the conversion
122 * is already done when we do this test
123 */
124 while ((i < 2) && mux_cnv) {
125 i++;
126 ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
127 mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
128 msleep_interruptible(1);
129 }
130
131 if (mux_cnv == 0) {
132 val = ads7871_read_reg16(spi, REG_LS_BYTE);
133 /*result in volts*10000 = (val/8192)*2.5*10000*/
134 val = ((val >> 2) * 25000) / 8192;
135 return sprintf(buf, "%d\n", val);
136 } else {
137 return -1;
138 }
139}
140
141static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0);
142static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1);
143static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2);
144static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3);
145static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4);
146static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5);
147static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6);
148static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7);
149
150static struct attribute *ads7871_attrs[] = {
151 &sensor_dev_attr_in0_input.dev_attr.attr,
152 &sensor_dev_attr_in1_input.dev_attr.attr,
153 &sensor_dev_attr_in2_input.dev_attr.attr,
154 &sensor_dev_attr_in3_input.dev_attr.attr,
155 &sensor_dev_attr_in4_input.dev_attr.attr,
156 &sensor_dev_attr_in5_input.dev_attr.attr,
157 &sensor_dev_attr_in6_input.dev_attr.attr,
158 &sensor_dev_attr_in7_input.dev_attr.attr,
159 NULL
160};
161
162ATTRIBUTE_GROUPS(ads7871);
163
164static int ads7871_probe(struct spi_device *spi)
165{
166 struct device *dev = &spi->dev;
167 int ret;
168 uint8_t val;
169 struct ads7871_data *pdata;
170 struct device *hwmon_dev;
171
172 /* Configure the SPI bus */
173 spi->mode = (SPI_MODE_0);
174 spi->bits_per_word = 8;
175 spi_setup(spi);
176
177 ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
178 ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
179
180 val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
181 ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
182 ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
183
184 dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
185 /*
186 * because there is no other error checking on an SPI bus
187 * we need to make sure we really have a chip
188 */
189 if (val != ret)
190 return -ENODEV;
191
192 pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL);
193 if (!pdata)
194 return -ENOMEM;
195
196 pdata->spi = spi;
197
198 hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
199 pdata,
200 ads7871_groups);
201 return PTR_ERR_OR_ZERO(hwmon_dev);
202}
203
204static struct spi_driver ads7871_driver = {
205 .driver = {
206 .name = DEVICE_NAME,
207 },
208 .probe = ads7871_probe,
209};
210
211module_spi_driver(ads7871_driver);
212
213MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
214MODULE_DESCRIPTION("TI ADS7871 A/D driver");
215MODULE_LICENSE("GPL");
216