• AD7170
• AD7171
• AD7780
• AD7781

• CN0107
• CN0108
• CN0188
• CN0218
• CN0240

• EVAL-AD7170EBZ
• EVAL-AD7171EBZ
• EVAL-AD7780EBZ
• EVAL-AD7781EBZ

This is a Linux industrial I/O (IIO) subsystem driver, targeting single channel serial interface ADCs. The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). See IIO for more information.

The reference voltage may vary between boards and models. The platform_data for the device's “struct device” holds this information.

static struct ad7780_platform_data __initdata ad7780_pdata = {
	.vref_mv  	= 2500,
	.gpio_pdrst	= GPIO_PF10,
};

Below example specifies a 3.3 Volt reference for the SPI device 3 on SPI-Bus 0. (spi0.3)

#if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
static struct regulator_consumer_supply ad7780_consumer_supplies[] = {
	REGULATOR_SUPPLY("vcc", "spi0.3"),
};
 
static struct regulator_init_data stamp_avdd_reg_init_data = {
	.constraints	= {
		.name	= "3V3",
		.valid_ops_mask = REGULATOR_CHANGE_STATUS,
	},
	.consumer_supplies = ad7780_consumer_supplies,
	.num_consumer_supplies = ARRAY_SIZE(ad7780_consumer_supplies),
};
 
static struct fixed_voltage_config stamp_vdd_pdata = {
	.supply_name	= "board-3V3",
	.microvolts	= 3300000,
	.gpio		= -EINVAL,
	.enabled_at_boot = 0,
	.init_data	= &stamp_avdd_reg_init_data,
};
static struct platform_device brd_voltage_regulator = {
	.name		= "reg-fixed-voltage",
	.id		= -1,
	.num_resources	= 0,
	.dev		= {
		.platform_data	= &stamp_vdd_pdata,
	},
};
#endif

static struct platform_device *board_devices[] __initdata = {
#if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
	&brd_voltage_regulator
#endif
};

static int __init board_init(void)
{
	[--snip--]
 
	platform_add_devices(board_devices, ARRAY_SIZE(board_devices));
 
	[--snip--]
 
	return 0;
}
arch_initcall(board_init);

Depending on the converter IC used, you may need to set the modalias accordingly, matching your part name. It may also required to adjust max_speed_hz. Please consult the datasheet, for maximum spi clock supported by the device in question.

static struct spi_board_info board_spi_board_info[] __initdata = {
#if defined(CONFIG_AD7780) || /
 	defined(CONFIG_AD7780_MODULE)
	{
		/* the modalias must be the same as spi device driver name */
		.modalias = "ad7780", /* Name of spi_driver for this device */
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0, /* Framework bus number */
		.chip_select = 3, /* Framework chip select */
		.platform_data = &ad7780_pdata,
		.irq = IRQ_PF6,
		.mode = SPI_MODE_0,
	},
#endif
};

static int __init board_init(void)
{
	[--snip--]
 
	spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info));
 
	[--snip--]
 
	return 0;
}
arch_initcall(board_init);

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

Linux Kernel Configuration
	Device Drivers  --->
		[*] Staging drivers  --->
			<*>     Industrial I/O support --->
			    --- Industrial I/O support
			    -*-   Enable ring buffer support within IIO
			    -*-     Industrial I/O lock free software ring
			    -*-   Enable triggered sampling support

			          *** Analog to digital converters ***
			    [--snip--]

			    <*>   Analog Devices AD7780 AD7781 ADC driver

			    [--snip--]

Description:
scale to be applied to in_voltage0_raw in order to obtain the measured voltage in millivolts.

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_scale
0.00029

Description:
Raw unscaled voltage measurement on channel 0

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in0_raw
-1

U = in_voltage0_raw * in_scale = -1 * 0.00029 = -0.00029 mV