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 /*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 72 struct ads7871_data { 73 struct device *hwmon_dev; 74 struct mutex update_lock; 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 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 } 135 136 static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0); 137 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1); 138 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2); 139 static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3); 140 static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4); 141 static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5); 142 static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6); 143 static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7); 144 145 static 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 }; 156 157 static const struct attribute_group ads7871_group = { 158 .attrs = ads7871_attributes, 159 }; 160 161 static int __devinit ads7871_probe(struct spi_device *spi) 162 { 163 int status, ret, err = 0; 164 uint8_t val; 165 struct ads7871_data *pdata; 166 167 dev_dbg(&spi->dev, "probe\n"); 168 169 pdata = kzalloc(sizeof(struct ads7871_data), GFP_KERNEL); 170 if (!pdata) { 171 err = -ENOMEM; 172 goto exit; 173 } 174 175 status = sysfs_create_group(&spi->dev.kobj, &ads7871_group); 176 if (status < 0) 177 goto error_free; 178 179 pdata->hwmon_dev = hwmon_device_register(&spi->dev); 180 if (IS_ERR(pdata->hwmon_dev)) { 181 err = PTR_ERR(pdata->hwmon_dev); 182 goto error_remove; 183 } 184 185 spi_set_drvdata(spi, pdata); 186 187 /* Configure the SPI bus */ 188 spi->mode = (SPI_MODE_0); 189 spi->bits_per_word = 8; 190 spi_setup(spi); 191 192 ads7871_write_reg8(spi, REG_SER_CONTROL, 0); 193 ads7871_write_reg8(spi, REG_AD_CONTROL, 0); 194 195 val = (OSC_OSCR_bm | OSC_OSCE_bm | OSC_REFE_bm | OSC_BUFE_bm); 196 ads7871_write_reg8(spi, REG_OSC_CONTROL, val); 197 ret = ads7871_read_reg8(spi, REG_OSC_CONTROL); 198 199 dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret); 200 /*because there is no other error checking on an SPI bus 201 we need to make sure we really have a chip*/ 202 if (val != ret) { 203 err = -ENODEV; 204 goto error_remove; 205 } 206 207 return 0; 208 209 error_remove: 210 sysfs_remove_group(&spi->dev.kobj, &ads7871_group); 211 error_free: 212 kfree(pdata); 213 exit: 214 return err; 215 } 216 217 static 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 } 226 227 static struct spi_driver ads7871_driver = { 228 .driver = { 229 .name = DEVICE_NAME, 230 .bus = &spi_bus_type, 231 .owner = THIS_MODULE, 232 }, 233 234 .probe = ads7871_probe, 235 .remove = __devexit_p(ads7871_remove), 236 }; 237 238 static int __init ads7871_init(void) 239 { 240 return spi_register_driver(&ads7871_driver); 241 } 242 243 static void __exit ads7871_exit(void) 244 { 245 spi_unregister_driver(&ads7871_driver); 246 } 247 248 module_init(ads7871_init); 249 module_exit(ads7871_exit); 250 251 MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>"); 252 MODULE_DESCRIPTION("TI ADS7871 A/D driver"); 253 MODULE_LICENSE("GPL"); 254