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AD9832 IIO直接数字合成Linux驱动程序

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This version (27 Apr 2016 17:13) was approved by Lars-Peter Clausen.The Previously approved version (11 Feb 2016 20:56) is available.

AD9832 IIO Direct Digital Synthesis Linux Driver
Source Code
- Status
- Files
Example platform device initialization
- Declaring SPI slave devices
Adding Linux driver support
Hardware configuration
Driver testing
More Information

AD9832 IIO Direct Digital Synthesis Linux Driver

Supported Devices

Evaluation Boards

EVAL-AD9832SDZ

Description

This is a Linux industrial I/O (IIO) subsystem driver, targeting serial interface DDS controllers. 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.

Source Code

Status

Source	Mainlined?
git	Yes

Files

Function	File
driver	drivers/staging/iio/frequency/ad9832.c
include	drivers/staging/iio/frequency/ad9832.h

Example platform device initialization

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

21 Oct 2010 16:10

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

/**
 * struct ad9832_platform_data - platform specific information
 * @mclk:		master clock in Hz
 * @freq0:		power up freq0 tuning word in Hz
 * @freq1:		power up freq1 tuning word in Hz
 * @phase0:		power up phase0 value [0..4095] correlates with 0..2PI
 * @phase1:		power up phase1 value [0..4095] correlates with 0..2PI
 * @phase2:		power up phase2 value [0..4095] correlates with 0..2PI
 * @phase3:		power up phase3 value [0..4095] correlates with 0..2PI
 */
 
struct ad9832_platform_data ad9832_pdata = {
	.mclk = 25000000,
	.freq0 = 1000000,
	.freq1 = 2000000,
	.phase0 = 512,
	.phase1 = 1024,
	.phase0 = 2048,
	.phase1 = 0,
 
};

Declaring SPI slave devices

Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.

This method is appropriate when the SPI bus is a system bus, as in many embedded systems, wherein each SPI bus has a number which is known in advance. It is thus possible to pre-declare the SPI devices that inhabit this bus. This is done with an array of struct spi_board_info, which is registered by calling spi_register_board_info().

For more information see: Documentation/spi/spi-summary

21 Oct 2010 16:10

Depending on the DDS 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_AD9832) /
	|| defined(CONFIG_AD9832_MODULE)
	{
		.modalias = "ad9832",
		.max_speed_hz = 1000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = 3, /* CS, change it for your board */
		.platform_data = &ad9832_pdata, /* No spi_driver specific config */
		.mode = SPI_MODE_2,
	},
#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);

Adding Linux driver support

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

The AD9832 Driver depends on CONFIG_SPI

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

			          *** Direct Digital Synthesis ***
			    [--snip--]

			    <*>   Analog Devices ad9832/5 driver

			    [--snip--]

Hardware configuration

Driver testing

Each and every IIO device, typically a hardware chip, has a device folder under /sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under every of these directory folders reside a set of files, depending on the characteristics and features of the hardware device in question. These files are consistently generalized and documented in the IIO ABI documentation. In order to determine which IIO deviceX corresponds to which hardware device, the user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case the sequence in which the iio device drivers are loaded/registered is constant, the numbering is constant and may be known in advance.

02 Mar 2011 15:16