• AD5380
• AD5381
• AD5382
• AD5383
• AD5384
• AD5390
• AD5391
• AD5392

• EVAL-AD5380EBZ
• EVAL-AD5382EBZ
• EVAL-AD5390EBZ
• EVAL-AD5391EBZ
• EVAL-AD5392EBZ

This is a Linux industrial I/O (IIO) subsystem driver, targeting multi-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 AD538X/AD539X can either use an internal or an external reference voltage. To use an external reference voltage use the regulator framework to provide a regulator supply. The supply should be called “vref”.

Below example specifies a 2.5 Volt reference for the SPI device 3 on SPI-Bus 0. (spi0.3)

#if IS_ENABLED(CONFIG_REGULATOR_FIXED_VOLTAGE)
static struct regulator_consumer_supply ad5380_consumer_supplies[] = {
	REGULATOR_SUPPLY("vref", "spi0.3"),
};
 
static struct regulator_init_data stamp_avdd_reg_init_data = {
	.constraints	= {
		.name	= "2V5",
		.valid_ops_mask = REGULATOR_CHANGE_STATUS,
	},
	.consumer_supplies = ad5380_consumer_supplies,
	.num_consumer_supplies = ARRAY_SIZE(ad5380_consumer_supplies),
};
 
static struct fixed_voltage_config stamp_vdd_pdata = {
	.supply_name	= "board-2V5",
	.microvolts	= 2500000,
	.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 IS_ENABLED(CONFIG_REGULATOR_FIXED_VOLTAGE)
	&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 IS_ENABLED(CONFIG_AD5380)
	{
		/* the modalias must be the same as spi device driver name */
		.modalias = "ad5380-5", /* 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 */
		.mode = SPI_MODE_1,
	},
#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);

Depending on the converter IC used, you may need to set the modalias accordingly, matching your part name.

The I2C device id depends on the AD0 and AD1 pin settings and needs to be set according to your board setup.

In this example we assume ADDR0=0 and ADDR1=0.

static struct i2c_board_info __initdata bfin_i2c_board_info[] = {
 
	[--snip--]
	{
		I2C_BOARD_INFO("a5380", 0x38),
	},
	[--snip--]
}

static int __init stamp_init(void)
{
	[--snip--]
	i2c_register_board_info(0, bfin_i2c_board_info,
				ARRAY_SIZE(bfin_i2c_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 AD5380/81/82/83/84/90/91/92 DAC driver
                ...
            ...
        ...

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

scale to be applied to out_voltageY_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
0.305000

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 10000 > out_voltage0_raw

U = out_voltage0_raw * out_voltage0_scale = 10000 * 0,305000 mV = 305,00 mV

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

Each channel has an adjustable gain which can be used to calibrate the channel's scale and compensate for full-scale errors. The default value is 16382. The minimum value is 0, the maximum value is 16383.

If scale calibration is used the following formula can be used calculate the output voltage:
U = ( ( out_voltageY_raw * ( out_voltageY_calibscale + 2) ) / 2^14 + out_voltageY_calibbias ) * out_voltageY_scale

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

Each channel has an adjustable offset which can be used to calibrate the channel's offset and compensate for zero-scale errors. The default value is 0. The minimum value is -8192, the maximum value is 8191.

If offset calibration is used the following formula can be used calculate the output voltage:
U = ( ( out_voltageY_raw * ( out_voltageY_calibscale + 2 ) ) / 2^14 + out_voltageY_calibbias ) * out_voltageY_scale

/sys/bus/iio/devices/iio:deviceX/out_voltage_powerdown

Description:
Writing 1 causes the device to enter power down mode. Clearing returns to normal operation.

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

/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
100kohm_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