diff options
Diffstat (limited to 'drivers/hwmon/ads7871.c')
| -rw-r--r-- | drivers/hwmon/ads7871.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c new file mode 100644 index 000000000..59bd7b9e1 --- /dev/null +++ b/drivers/hwmon/ads7871.c @@ -0,0 +1,215 @@ +/* + * ads7871 - driver for TI ADS7871 A/D converter + * + * Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com> + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 or + * later as publishhed by the Free Software Foundation. + * + * You need to have something like this in struct spi_board_info + * { + * .modalias = "ads7871", + * .max_speed_hz = 2*1000*1000, + * .chip_select = 0, + * .bus_num = 1, + * }, + */ + +/*From figure 18 in the datasheet*/ +/*Register addresses*/ +#define REG_LS_BYTE 0 /*A/D Output Data, LS Byte*/ +#define REG_MS_BYTE 1 /*A/D Output Data, MS Byte*/ +#define REG_PGA_VALID 2 /*PGA Valid Register*/ +#define REG_AD_CONTROL 3 /*A/D Control Register*/ +#define REG_GAIN_MUX 4 /*Gain/Mux Register*/ +#define REG_IO_STATE 5 /*Digital I/O State Register*/ +#define REG_IO_CONTROL 6 /*Digital I/O Control Register*/ +#define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/ +#define REG_SER_CONTROL 24 /*Serial Interface Control Register*/ +#define REG_ID 31 /*ID Register*/ + +/* + * From figure 17 in the datasheet + * These bits get ORed with the address to form + * the instruction byte + */ +/*Instruction Bit masks*/ +#define INST_MODE_BM (1 << 7) +#define INST_READ_BM (1 << 6) +#define INST_16BIT_BM (1 << 5) + +/*From figure 18 in the datasheet*/ +/*bit masks for Rev/Oscillator Control Register*/ +#define MUX_CNV_BV 7 +#define MUX_CNV_BM (1 << MUX_CNV_BV) +#define MUX_M3_BM (1 << 3) /*M3 selects single ended*/ +#define MUX_G_BV 4 /*allows for reg = (gain << MUX_G_BV) | ...*/ + +/*From figure 18 in the datasheet*/ +/*bit masks for Rev/Oscillator Control Register*/ +#define OSC_OSCR_BM (1 << 5) +#define OSC_OSCE_BM (1 << 4) +#define OSC_REFE_BM (1 << 3) +#define OSC_BUFE_BM (1 << 2) +#define OSC_R2V_BM (1 << 1) +#define OSC_RBG_BM (1 << 0) + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/spi/spi.h> +#include <linux/hwmon.h> +#include <linux/hwmon-sysfs.h> +#include <linux/err.h> +#include <linux/delay.h> + +#define DEVICE_NAME "ads7871" + +struct ads7871_data { + struct spi_device *spi; +}; + +static int ads7871_read_reg8(struct spi_device *spi, int reg) +{ + int ret; + reg = reg | INST_READ_BM; + ret = spi_w8r8(spi, reg); + return ret; +} + +static int ads7871_read_reg16(struct spi_device *spi, int reg) +{ + int ret; + reg = reg | INST_READ_BM | INST_16BIT_BM; + ret = spi_w8r16(spi, reg); + return ret; +} + +static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val) +{ + u8 tmp[2] = {reg, val}; + return spi_write(spi, tmp, sizeof(tmp)); +} + +static ssize_t show_voltage(struct device *dev, + struct device_attribute *da, char *buf) +{ + struct ads7871_data *pdata = dev_get_drvdata(dev); + struct spi_device *spi = pdata->spi; + struct sensor_device_attribute *attr = to_sensor_dev_attr(da); + int ret, val, i = 0; + uint8_t channel, mux_cnv; + + channel = attr->index; + /* + * TODO: add support for conversions + * other than single ended with a gain of 1 + */ + /*MUX_M3_BM forces single ended*/ + /*This is also where the gain of the PGA would be set*/ + ads7871_write_reg8(spi, REG_GAIN_MUX, + (MUX_CNV_BM | MUX_M3_BM | channel)); + + ret = ads7871_read_reg8(spi, REG_GAIN_MUX); + mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); + /* + * on 400MHz arm9 platform the conversion + * is already done when we do this test + */ + while ((i < 2) && mux_cnv) { + i++; + ret = ads7871_read_reg8(spi, REG_GAIN_MUX); + mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); + msleep_interruptible(1); + } + + if (mux_cnv == 0) { + val = ads7871_read_reg16(spi, REG_LS_BYTE); + /*result in volts*10000 = (val/8192)*2.5*10000*/ + val = ((val >> 2) * 25000) / 8192; + return sprintf(buf, "%d\n", val); + } else { + return -1; + } +} + +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0); +static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1); +static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2); +static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3); +static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4); +static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5); +static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6); +static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7); + +static struct attribute *ads7871_attrs[] = { + &sensor_dev_attr_in0_input.dev_attr.attr, + &sensor_dev_attr_in1_input.dev_attr.attr, + &sensor_dev_attr_in2_input.dev_attr.attr, + &sensor_dev_attr_in3_input.dev_attr.attr, + &sensor_dev_attr_in4_input.dev_attr.attr, + &sensor_dev_attr_in5_input.dev_attr.attr, + &sensor_dev_attr_in6_input.dev_attr.attr, + &sensor_dev_attr_in7_input.dev_attr.attr, + NULL +}; + +ATTRIBUTE_GROUPS(ads7871); + +static int ads7871_probe(struct spi_device *spi) +{ + struct device *dev = &spi->dev; + int ret; + uint8_t val; + struct ads7871_data *pdata; + struct device *hwmon_dev; + + /* Configure the SPI bus */ + spi->mode = (SPI_MODE_0); + spi->bits_per_word = 8; + spi_setup(spi); + + ads7871_write_reg8(spi, REG_SER_CONTROL, 0); + ads7871_write_reg8(spi, REG_AD_CONTROL, 0); + + val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM); + ads7871_write_reg8(spi, REG_OSC_CONTROL, val); + ret = ads7871_read_reg8(spi, REG_OSC_CONTROL); + + dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret); + /* + * because there is no other error checking on an SPI bus + * we need to make sure we really have a chip + */ + if (val != ret) + return -ENODEV; + + pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL); + if (!pdata) + return -ENOMEM; + + pdata->spi = spi; + + hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias, + pdata, + ads7871_groups); + return PTR_ERR_OR_ZERO(hwmon_dev); +} + +static struct spi_driver ads7871_driver = { + .driver = { + .name = DEVICE_NAME, + }, + .probe = ads7871_probe, +}; + +module_spi_driver(ads7871_driver); + +MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>"); +MODULE_DESCRIPTION("TI ADS7871 A/D driver"); +MODULE_LICENSE("GPL"); |