• AD5760
• AD5780
• AD5781
• AD5790
• AD5791

• CN0177
• CN0191
• CN0200
• CN0257
• CN0278
• CN0318

• EVAL-AD5760SDZ
• EVAL-AD5780SDZ
• EVAL-AD5781SDZ
• EVAL-AD5790SDZ
• EVAL-AD5791SDZ

This is a Linux industrial I/O (IIO) subsystem driver, targeting single-channel serial interface DACs. 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.

/**
 * struct ad5791_platform_data - platform specific information
 * @vref_pos_mv:	Vdd Positive Analog Supply Volatge (mV)
 * @vref_neg_mv:	Vdd Negative Analog Supply Volatge (mV)
 * @use_rbuf_gain2:	ext. amplifier connected in gain of two configuration
 */
 
struct ad5791_platform_data {
	u16				vref_pos_mv;
	u16				vref_neg_mv;
	bool				use_rbuf_gain2;
};

Below example specifies a 30 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 ad5791_consumer_supplies_vdd[] = {
	REGULATOR_SUPPLY("vdd", "spi0.3"),
};
 
static struct regulator_init_data stamp_avdd_reg_init_data = {
	.constraints	= {
		.name	= "10V0",
		.valid_ops_mask = REGULATOR_CHANGE_STATUS,
	},
	.consumer_supplies = ad5791_consumer_supplies_vdd,
	.num_consumer_supplies = ARRAY_SIZE(ad5791_consumer_supplies_vdd),
};
 
static struct fixed_voltage_config stamp_vdd_pdata = {
	.supply_name	= "board+10V0",
	.microvolts	= 10000000,
	.gpio		= -EINVAL,
	.enabled_at_boot = 0,
	.init_data	= &stamp_avdd_reg_init_data,
};
static struct platform_device brd_voltage_regulator_vdd = {
	.name		= "reg-fixed-voltage",
	.id		= 0,
	.num_resources	= 0,
	.dev		= {
		.platform_data	= &stamp_vdd_pdata,
	},
};
 
static struct regulator_consumer_supply ad5791_consumer_supplies_vss[] = {
	REGULATOR_SUPPLY("vss", "spi0.3"),
};
 
static struct regulator_init_data stamp_avss_reg_init_data = {
	.constraints	= {
		.name	= "-10V0",
		.valid_ops_mask = REGULATOR_CHANGE_STATUS,
	},
	.consumer_supplies = ad5791_consumer_supplies_vss,
	.num_consumer_supplies = ARRAY_SIZE(ad5791_consumer_supplies_vss),
};
 
static struct fixed_voltage_config stamp_vss_pdata = {
	.supply_name	= "board-10V0",
	.microvolts	= 10000000,
	.gpio		= -EINVAL,
	.enabled_at_boot = 0,
	.init_data	= &stamp_avss_reg_init_data,
};
static struct platform_device brd_voltage_regulator_vss = {
	.name		= "reg-fixed-voltage",
	.id		= 1,
	.num_resources	= 0,
	.dev		= {
		.platform_data	= &stamp_vss_pdata,
	},
};
#endif

static struct platform_device *board_devices[] __initdata = {
#if defined(CONFIG_REGULATOR_FIXED_VOLTAGE) || defined(CONFIG_REGULATOR_FIXED_VOLTAGE_MODULE)
	&brd_voltage_regulator_vss,
	&brd_voltage_regulator_vdd,
#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_AD5791) || /
 	defined(CONFIG_AD5791
_MODULE)
	{
		/* the modalias must be the same as spi device driver name */
		.modalias = "ad5791", /* 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 = &ad5791_pdata,
		.mode = SPI_MODE_3,
	},
#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  --->
        ...
        <*>     Industrial I/O support --->
            --- Industrial I/O support
            ...
            Digital to analog converters  ---> 
                ...
                <*>   Analog Devices AD5760/AD5780/AD5781/AD5790/AD5791 DAC SPI driver
                ...
            ...
        ...

Description:
scale to be applied to out_voltage0_raw in order to obtain the measured voltage in millivolts.

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> cat out_voltage_scale
0.019

Description:
/sys/bus/iio/devices/iio:deviceX/out_voltageY_raw

Raw (unscaled, no bias etc.) output voltage for channel Y.

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> echo 131579 > out_voltage0_raw

U = out_voltage0_raw * out_voltage_scale = 131579 * 0.019 = 2500.001 mV

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> echo -131579 > out_voltage0_raw

U = out_voltage0_raw * out_voltage_scale = -131579 * 0.019 = -2500.001 mV

/sys/bus/iio/devices/iio:deviceX/out_voltage_powerdown_mode_available

Description:
Lists all available output power down modes.

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> cat out_voltage_powerdown_mode_available
6kohm_to_gnd three_state

/sys/bus/iio/devices/iio:deviceX/out_voltage_powerdown_mode

Description:
Specifies the output power down mode. DAC output stage is disconnected from the amplifier and

For a list of available output power down options read out_voltage_powerdown_mode_available.

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> echo three_state > out_voltage_powerdown_mode
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> cat out_voltage_powerdown_mode
three_state

/sys/bus/iio/devices/iio:deviceX/out_voltageY_powerdown

Description:
Writing 1 causes output Y to enter the power down mode specified by the corresponding out_voltageY_powerdown_mode. Clearing returns to normal operation. Y may be suppressed if all outputs are controlled together.

root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> echo 1 > out_voltage0_powerdown
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> cat out_voltage0_powerdown
1
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> echo 0 > out_voltage0_powerdown
root:/sys/devices/platform/bfin-spi.0/spi0.3/iio:device0> cat out_voltage0_powerdown
0