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This version (19 Jan 2018 09:58) was approved by aardelean.The Previously approved version (12 Jul 2017 08:20) is available.Diff

AXI ADC HDL Linux Driver

Supported Devices

Supported Boards

Description

The AXI ADC HDL driver is the driver for Generic AXI ADC IP core which is used on various FPGA designs. The driver is implemented as an Linux IIO driver. It's register map can be found here: Base register map (common to all cores)

This driver is split into two parts. A control driver let’s call it SPI-ADC which configures the converter internal control registers, this part is typically instantiated via the SPI bus. (see: ad9467.c, ad9361_conv.c or ad9371_conv.c) Device probing for the data capture driver (AXI-ADC) which controls the AXI HDL core registers and the DMA, is delayed until the SPI control driver is fully probed. The device tree phandle “spibus-connected” is used to connect the capture driver with is SPI control driver. This split is required since the AXI-ADC and the SPI-ADC parts are instantiated via different busses. The AXI-ADC driver registers the IIO device, the SPI-ADC instance doesn’t. However a shared data structure (struct axiadc_converter) is used so that the methods local to the SPI-ADC driver can extend the IIO attributes provided the AXI-ADC driver. There is also a callback provided (post_setup) which calls a from the AXI-ADC into the AXI-SPI driver after the AXI-ADC is fully alive. This post setup callback is then typically used to finally configure the digital data path, test and tune the digital data interface etc.

For the AD9361 and AD9371 family of transceivers, things are a bit more differentiated. In fact these devices have a separate IIO device for the radio control portion. We call them the PHY devices. ( ad9361.c and ad9371.c ) The PHY drivers are intended to be independent from our AXI-ADC capture drivers and underlying HDL designs. Therefore things related to the AXI-ADC driver are located in the ad93X1_conv.c files.

Source Code

Status

Files

Example platform device initialization

The AXI ADC driver is a platform driver and can currently only be instantiated via device tree.

Required devicetree properties:

  • compatible: Should always be one of these:
    • “xlnx,cf-ad9467-core-1.00.a”
    • “xlnx,axi-adc-1c-1.00.a”
    • “xlnx,axi-ad9234-1.00.a”
    • “xlnx,axi-ad9250-1.00.a”
    • “xlnx,axi-ad9434-1.00.a”
    • “adi,axi-ad9643-6.00.a”
    • “adi,axi-ad9361-6.00.a”
    • “adi,axi-ad9371-6.00.a”
    • “adi,axi-ad9680-1.0”
    • “adi,axi-ad9625-1.0”
    • “adi,axi-ad6676-1.0”
    • “adi,axi-ad9684-1.0”
    • For a complete list see driver source: static const struct of_device_id axiadc_of_match[]
  • reg: Base address and register area size. This parameter expects a register range.
  • spibus-connected: Phandle to the SPI device on which the AD9467/AD9643 can be found
  • dmas: List of DMA controller phandle. DMA specifiers for tx and rx dma. See the DMA client binding, Documentation/devicetree/bindings/dma/dma.txt
  • dma-names: DMA request names should include “tx” and “rx” if present.

Example:

&fmc_spi {
	adc_ad9467: ad9467@0 {
		#address-cells = <1>;
		#size-cells = <0>;
		compatible = "ad9467";
		reg = <0>;
		spi-max-frequency = <10000000>;
		clocks = <&clk_ad9517 3>;
		clock-names = "adc_clk";

		adi,spi-3wire-enable;
	};
};

&fpga_axi {
	rx_dma: rx-dmac@44A30000 {
		compatible = "adi,axi-dmac-1.00.a";
		reg = <0x44A30000 0x10000>;
		#dma-cells = <1>;
		interrupts = <0 57 0>;
		clocks = <&clkc 16>;

		dma-channel {
			adi,type = <0>;
		};
	};

	cf_ad9467_core_0: cf-ad9467-core-lpc@44A00000 {
		compatible = "xlnx,cf-ad9467-core-1.00.a";
		reg = <0x44A00000 0x10000>;
		dmas = <&rx_dma 0>;
		dma-names = "rx";
		spibus-connected = <&adc_ad9467>;
	} ;
};

Enabling Linux driver support

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

The AXI ADC HDL driver depends on CONFIG_SPI

Adding Linux driver support

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
	    -*-   Enable ring buffer support within IIO
	    -*-     Industrial I/O lock free software ring
	    -*-   Enable triggered sampling support

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

		<*>   Analog Devices AD9467 AD9643 High-Speed AXI ADC 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

This specifies any shell prompt running on the target

root:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
iio:device4  iio:trigger0

root:/sys/bus/iio/devices> cd iio:device4

root:/sys/bus/iio/devices/iio:device4> ls -l
drwxr-xr-x    2 root     root             0 Jan  1 00:00 buffer
-r--r--r--    1 root     root          4096 Jan  1 00:00 dev
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage0_calibbias
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage0_calibphase
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage0_calibscale
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage0_filter_high_pass_3db_frequency
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage0_test_mode
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage1_calibbias
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage1_calibphase
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage1_calibscale
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage1_filter_high_pass_3db_frequency
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage1_test_mode
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage_sampling_frequency
-rw-r--r--    1 root     root          4096 Jan  1 00:00 in_voltage_scale
-r--r--r--    1 root     root          4096 Jan  1 00:00 in_voltage_scale_available
-r--r--r--    1 root     root          4096 Jan  1 00:00 in_voltage_test_mode_available
-r--r--r--    1 root     root          4096 Jan  1 00:00 name
drwxr-xr-x    2 root     root             0 Jan  1 00:00 scan_elements
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 subsystem -> ../../../../bus/iio
-rw-r--r--    1 root     root          4096 Jan  1 00:00 uevent
root:/sys/bus/iio/devices/iio:device4>

Show device name

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> cat name
cf-ad9643-core-lpc

Show scale

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

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> cat in_voltage_scale
0.026703

Show available scales

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> cat in_voltage_scale_available
0.031738 0.031403 0.031067 0.030731 0.030396 0.030060 0.029724 0.029388 0.029053 0.028717 0.028381 0.028046 0.027710 0.027374 0.027039 0.026703 0.026367 0.026031 0.025696 0.025360 0.025024 0.024689 0.024353 0.024017 0.023682 0.023346 0.023010 0.022675 0.022339 0.022003 0.021667 0.021332

Set ADC calibration gain

Description:
in_voltage0_calibscale
in_voltage1_calibscale

Set the channel calibration gain. Writing to these files will set the calibration gain for the respective channel. Valid values are in the range of 0..1.999999

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> cat in_voltage0_calibscale
1.000000

Set ADC calibration bias

Description:
in_voltage0_calibbias
in_voltage1_calibbias

Set the channel calibration bias/offset. Writing to these files will set the calibration bias for the respective channel. Valid values are in the range of +/- 16384.

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> cat in_voltage0_calibscale
1.0

Show available ADC test modes

Description:

Show available test modes supported by the underlying ADC. These test modes are typically used to test the high speed digital interface between the converter and interface adaptor.

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> cat in_voltage_test_mode_available
off midscale_short pos_fullscale neg_fullscale checkerboard pn_long pn_short one_zero_toggle

Set ADC test mode

Description:
in_voltage0_test_mode
in_voltage1_test_mode

Enter test modes supported by the underlying ADC. These test modes are typically used to test the high speed digital interface between the converter and interface adaptor.

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4> echo one_zero_toggle > in_voltage0_test_mode
root:/sys/bus/iio/devices/iio:device4> cat in_voltage0_test_mode
one_zero_toggle
root:/sys/bus/iio/devices/iio:device4> echo off > in_voltage0_test_mode

in_voltage0_test_mode:off

Buffer management

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4/buffer> ls
bytes_per_datum          enable                   subsystem
length                   uevent
root:/sys/bus/iio/devices/iio:device4/buffer>

The Industrial I/O subsystem provides support for various ring buffer based data acquisition methods. Apart from device specific hardware buffer support, the user can chose between two different software ring buffer implementations. One is the IIO lock free software ring, and the other is based on Linux kfifo. Devices with buffer support feature an additional sub-folder in the /sys/bus/iio/devices/deviceX/ folder hierarchy. Called deviceX:bufferY, where Y defaults to 0, for devices with a single buffer.

Every buffer implementation features a set of files:

length
Get/set the number of sample sets that may be held by the buffer.

enable
Enables/disables the buffer. This file should be written last, after length and selection of scan elements.

scan_elements
The scan_elements directory contains interfaces for elements that will be captured for a single triggered sample set in the buffer.

02 Mar 2011 15:16

This specifies any shell prompt running on the target

root:/sys/bus/iio/devices/iio:device4/scan_elements> ls
in_voltage0_en         
in_voltage0_index      
in_voltage0_type 
in_voltage1_en         
in_voltage1_index      
in_voltage1_type        
root:/sys/bus/iio/devices/iio:device4/scan_elements>

in_voltageX_en / in_voltageX-voltageY_en / timestamp_en:
Scan element control for triggered data capture. Writing 1 will enable the scan element, writing 0 will disable it

in_voltageX_type / in_voltageX-voltageY_type / timestamp_type:
Description of the scan element data storage within the buffer and therefore in the form in which it is read from user-space. Form is [s|u]bits/storage-bits. s or u specifies if signed (2's complement) or unsigned. bits is the number of bits of data and storage-bits is the space (after padding) that it occupies in the buffer. Note that some devices will have additional information in the unused bits so to get a clean value, the bits value must be used to mask the buffer output value appropriately. The storage-bits value also specifies the data alignment. So u12/16 will be a unsigned 12 bit integer stored in a 16 bit location aligned to a 16 bit boundary. For other storage combinations this attribute will be extended appropriately.

in_voltageX_index / in_voltageX-voltageY_index / timestamp_index:
A single positive integer specifying the position of this scan element in the buffer. Note these are not dependent on what is enabled and may not be contiguous. Thus for user-space to establish the full layout these must be used in conjunction with all _en attributes to establish which channels are present, and the relevant _type attributes to establish the data storage format.

02 Mar 2011 15:16

More Information

resources/tools-software/linux-drivers/iio-adc/axi-adc-hdl.txt · Last modified: 19 Jan 2018 09:58 by aardelean