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 73 struct ads7871_data { 74 struct spi_device *spi; 75 }; 76 77 static 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 85 static 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 93 static 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 99 static 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 } 140 141 static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0); 142 static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1); 143 static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2); 144 static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3); 145 static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4); 146 static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5); 147 static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6); 148 static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7); 149 150 static 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 }; 161 162 ATTRIBUTE_GROUPS(ads7871); 163 164 static 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 } 203 204 static struct spi_driver ads7871_driver = { 205 .driver = { 206 .name = DEVICE_NAME, 207 }, 208 .probe = ads7871_probe, 209 }; 210 211 module_spi_driver(ads7871_driver); 212 213 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>"); 214 MODULE_DESCRIPTION("TI ADS7871 A/D driver"); 215 MODULE_LICENSE("GPL"); 216