AD2S1210

AD2S1210 IIO Resolver-to-Digital Converter.

Supported Devices

Evaluation Boards

Reference Circuits

Description

This is a Linux industrial I/O (Linux Industrial I/O Subsystem) subsystem driver, targeting Resolver-to-Digital Converters. 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 Linux Industrial I/O Subsystem for more information.

Source Code

Status

Source

Mainlined?

git

Yes

Support for the AD2S1210 is in mainline for kernel v6.7 and is backported to v6.1 of the ADI tree. Some additional features are slated for v6.8. The device was previously supported by a staging driver with a different ABI.

Files

Function

File

driver

drivers/iio/resolver/ad2s1210.c

devicetree

Documentation/devicetree/bindings/iio/resolver/adi,ad2s1210.yaml

Adding Linux driver support

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

Note

The 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

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

                <*>   Analog Devices AD2S1210 driver

                [--snip--]

Driver Usage

To configure the chip, use the attributes according to the device register to IIO ABI mapping below:

Register

Addr

IIO ABI (sysfs)

Units

Notes

DOS Overrange Threshold

0x89

events/in_altvoltage0_thresh_rising_value

mV

DOS Mismatch Threshold

0x8A

events/in_altvoltage0_mag_rising_value

mV

DOS Reset Maximum Threshold

0x8B

events/in_altvoltage0_mag_rising_reset_max

mV

DOS Reset Minimum Threshold

0x8C

events/in_altvoltage0_mag_rising_reset_min

mV

LOT High Threshold

0x8D

events/in_angl1_thresh_rising_value

Radians

LOT Low Threshold

0x8E

events/in_angl1_thresh_rising_hysteresis

Radians

The value written to the LOT low register is high value minus the hysteresis.

Excitation Frequency

0x91

out_altvoltage0_frequency

Hz

Control

0x92

*as bit fields*

Phase lock range

D5

events/in_phase0_mag_rising_value

Radians

Hysteresis

D4

in_angl0_hysteresis

Convert to radians by multiplying channel scale

Encoder resolution

D3:2

*not implemented*

Resolution

D1:0

*device tree: assigned-resolution-bits*

Bits

10, 12, 14, or 16

Soft Reset

0xF0

Soft reset is performed when `out_altvoltage0_frequency` is written.

Fault

0xFF

*not implemented*

Interfacing With the AD2S1210 via iio_attr

Accessing a list of channels:

analog@setup-2-zed:~ $ iio_attr ad2s1210 -c
dev 'ad2s1210', channel 'angl0' (input, index: 0, format: be:U16/16>>0), found 5 channel-specific attributes
dev 'ad2s1210', channel 'anglvel0' (input, index: 1, format: be:S16/16>>0), found 3 channel-specific attributes
dev 'ad2s1210', channel 'timestamp' (input, index: 2, format: le:S64/64>>0), found 0 channel-specific attributes
dev 'ad2s1210', channel 'phase0' (input), found 1 channel-specific attributes
dev 'ad2s1210', channel 'altvoltage0' (output), found 3 channel-specific attributes
dev 'ad2s1210', channel 'altvoltage2' (input), found 1 channel-specific attributes
dev 'ad2s1210', channel 'angl1' (input), found 1 channel-specific attributes
dev 'ad2s1210', channel 'altvoltage0' (input), found 1 channel-specific attributes
dev 'ad2s1210', channel 'altvoltage1' (input), found 1 channel-specific attributes

For example, to get position channel angl0:

analog@setup-2-zed:~ $ iio_attr ad2s1210 -ci angl0
dev 'ad2s1210', channel 'angl0' (input), attr 'hysteresis', value '1'
dev 'ad2s1210', channel 'angl0' (input), attr 'hysteresis_available', value
'0 1'
dev 'ad2s1210', channel 'angl0' (input), attr 'label', value 'position'
dev 'ad2s1210', channel 'angl0' (input), attr 'raw', value '34114'
dev 'ad2s1210', channel 'angl0' (input), attr 'scale', value '0.000095874'

Or velocity channel anglvel0:

analog@setup-2-zed:~ $ iio_attr ad2s1210 -ci anglvel0
dev 'ad2s1210', channel 'anglvel0' (input), attr 'label', value 'velocity'
dev 'ad2s1210', channel 'anglvel0' (input), attr 'raw', value '0'
dev 'ad2s1210', channel 'anglvel0' (input), attr 'scale', value '0.023968449'

Interfacing With the AD2S1210 via /sys/bus

Alternatively, you can read and write data directly from the device path in /sys/bus:

analog@setup-2-zed:~ $ cd /sys/bus/iio/devices/iio\:device1/

analog@setup-2-zed:/sys/bus/iio/devices/iio:device1 $ tree
.
├── buffer
│   ├── data_available
│   ├── direction
│   ├── enable
│   ├── length
│   └── watermark
├── buffer0
│   ├── data_available
│   ├── direction
│   ├── enable
│   ├── in_angl0_en
│   ├── in_angl0_index
│   ├── in_angl0_type
│   ├── in_anglvel0_en
│   ├── in_anglvel0_index
│   ├── in_anglvel0_type
│   ├── in_timestamp_en
│   ├── in_timestamp_index
│   ├── in_timestamp_type
│   ├── length
│   └── watermark
├── current_timestamp_clock
├── dev
├── events
│   ├── in_altvoltage0_mag_rising_label
│   ├── in_altvoltage0_mag_rising_reset_max
│   ├── in_altvoltage0_mag_rising_reset_max_available
│   ├── in_altvoltage0_mag_rising_reset_min
│   ├── in_altvoltage0_mag_rising_reset_min_available
│   ├── in_altvoltage0_mag_rising_value
│   ├── in_altvoltage0_mag_rising_value_available
│   ├── in_altvoltage0_thresh_falling_label
│   ├── in_altvoltage0_thresh_falling_value
│   ├── in_altvoltage0_thresh_falling_value_available
│   ├── in_altvoltage0_thresh_rising_label
│   ├── in_altvoltage0_thresh_rising_value
│   ├── in_altvoltage0_thresh_rising_value_available
│   ├── in_altvoltage1_mag_either_label
│   ├── in_altvoltage2_mag_either_label
│   ├── in_angl1_thresh_rising_hysteresis
│   ├── in_angl1_thresh_rising_hysteresis_available
│   ├── in_angl1_thresh_rising_label
│   ├── in_angl1_thresh_rising_value
│   ├── in_angl1_thresh_rising_value_available
│   ├── in_anglvel0_mag_rising_label
│   ├── in_phase0_mag_rising_label
│   ├── in_phase0_mag_rising_value
│   └── in_phase0_mag_rising_value_available
├── in_altvoltage0_label
├── in_altvoltage1_label
├── in_altvoltage2_label
├── in_angl0_hysteresis
├── in_angl0_hysteresis_available
├── in_angl0_label
├── in_angl0_raw
├── in_angl0_scale
├── in_angl1_label
├── in_anglvel0_label
├── in_anglvel0_raw
├── in_anglvel0_scale
├── in_phase0_label
├── name
├── of_node -> ../../../../../../../../firmware/devicetree/base/axi/spi@e0006000/ad2s1210@0
├── out_altvoltage0_frequency
├── out_altvoltage0_frequency_available
├── out_altvoltage0_label
├── power
│   ├── autosuspend_delay_ms
│   ├── control
│   ├── runtime_active_time
│   ├── runtime_status
│   └── runtime_suspended_time
├── scan_elements
│   ├── in_angl0_en
│   ├── in_angl0_index
│   ├── in_angl0_type
│   ├── in_anglvel0_en
│   ├── in_anglvel0_index
│   ├── in_anglvel0_type
│   ├── in_timestamp_en
│   ├── in_timestamp_index
│   └── in_timestamp_type
├── subsystem -> ../../../../../../../../bus/iio
├── trigger
│   └── current_trigger
├── uevent
└── waiting_for_supplier

analog@setup-2-zed:/sys/bus/iio/devices/iio:device1 $ cat name
ad2s1210

analog@setup-2-zed:/sys/bus/iio/devices/iio:device1 $ cat in_angl0_raw
34115

Hysteresis can be enabled or disabled this way. To do so, first check the output of in_angl0_hysteresis_available:

root@setup-2-zed:/sys/bus/iio/devices/iio:device1# cat in_angl0_hysteresis_available
0 1

To turn hysteresis off, write the first value from the output to in_angl0_hysteresis:

root@setup-2-zed:/sys/bus/iio/devices/iio:device1# echo 0 > in_angl0_hysteresis

To turn it on, write the second value (which is dependent on the assigned bits for resolution and may not always be 1):

root@setup-2-zed:/sys/bus/iio/devices/iio:device1# echo 1 > in_angl0_hysteresis

Triggered buffer

To generate samples using the triggered buffer, you will need a trigger. You can create an hrtimer trigger and test it by retrieving samples like this:

root@setup-2-zed:~# mkdir /sys/kernel/config/iio/triggers/hrtimer/test
root@setup-2-zed:~# iio_readdev ad2s1210 -t test -s 1000 -T 10000 | hd
WARNING: High-speed mode not enabled
00000000  85 41 00 00 00 00 00 00  82 e1 7d ad 09 54 9e 17  |.A........}..T..|
00000010  85 41 00 00 00 00 00 00  00 70 16 ae 09 54 9e 17  |.A.......p...T..|
00000020  85 42 00 00 00 00 00 00  5f 06 af ae 09 54 9e 17  |.B......_....T..|
00000030  85 41 00 00 00 00 00 00  3f a2 47 af 09 54 9e 17  |.A......?.G..T..|
00000040  85 42 00 00 00 00 00 00  7f 32 e0 af 09 54 9e 17  |.B.......2...T..|
00000050  85 41 00 00 00 00 00 00  41 c8 78 b0 09 54 9e 17  |.A......A.x..T..|
00000060  85 41 00 00 00 00 00 00  ab 64 11 b1 09 54 9e 17  |.A.......d...T..|
00000070  85 41 00 00 00 00 00 00  fb f6 a9 b1 09 54 9e 17  |.A...........T..|
00000080  85 41 00 00 00 00 00 00  85 8b 42 b2 09 54 9e 17  |.A........B..T..|
00000090  85 41 ff ff 00 00 00 00  13 22 db b2 09 54 9e 17  |.A......."...T..|
000000a0  85 42 00 00 00 00 00 00  e3 b8 73 b3 09 54 9e 17  |.B........s..T..|
000000b0  85 42 00 00 00 00 00 00  53 4f 0c b4 09 54 9e 17  |.B......SO...T..|
000000c0  85 41 00 00 00 00 00 00  6a e8 a4 b4 09 54 9e 17  |.A......j....T..|
000000d0  85 41 00 00 00 00 00 00  24 7d 3d b5 09 54 9e 17  |.A......$}=..T..|
000000e0  85 41 ff ff 00 00 00 00  7c 13 d6 b5 09 54 9e 17  |.A......|....T..|
000000f0  85 41 00 00 00 00 00 00  2c a9 6e b6 09 54 9e 17  |.A......,.n..T..|
...

Important

using the -t option to specify the trigger with iio_readdev resets the sampling rate of the hrtimer trigger back to 100Hz!

For other apps, we probably want a high sample rate. You can change the rate like this:

root@setup-2-zed:~# iio_attr -d test sampling_frequency 10000
10000.000000

Reading IIO Events

See iio_event_monitor for an example of a program designed to read IIO events.

Fault to event mapping:

Fault

Channel

Type

Direction

Notes

Sine/cosine inputs clipped

D7

altvoltage1

mag

either

The chip does not differentiate between fault on sine vs. cosine so there will also be an event on the altvoltage2 channel.

Sine/cosine inputs below LOS

D6

altvoltage0

thresh

falling

Sine/cosine inputs exceed DOS overrange

D5

altvoltage0

thresh

rising

Sine/cosine inputs exceed DOS mismatch

D4

altvoltage0

mag

rising

Tracking error exceeds LOT

D3

angl1

thresh

rising

Velocity exceeds maximum tracking rate

D2

anglvel0

mag

rising

Phase error exceeds phase lock range

D1

phase0

mag

rising

Configuration parity error

D0

*writes to kernel log*

Usage With the EVAL-AD2S1210SDZ Evaluation Board

Interfacing With a Raspberry Pi

Wiring

AD2S1210 Pin

Eval Board Pin

RPi Header Pin

RPi Function

Notes

RES0

LK6

15

GPIO22

There aren’t J4 pins for RES0/1 so have to use jumper pins. It is also possible to hard-wire resolution pins RES0/1, but device tree would need to be changed accordingly.

RES1

LK7

16

GPIO23

There aren’t J4 pins for RES0/1 so have to use jumper pins. It is also possible to hard-wire resolution pins RES0/1, but device tree would need to be changed accordingly.

A0

J4-12

18

GPIO24

A1

J4-11

22

GPIO25

WR/FSYNC

J4-4

24

SPI0 CE0

SAMPLE

J4-1

12

GPIO18

VDRIVE

J704-1

1

3.3V

DGND

J704-2

9

GND

SCLK

J4-10

23

SPI0 SCLK

SDI

J4-9

19

SPI0 MOSI

SDO

J4-8

21

SPI0 MISO

AD2S1210 Pin

Eval Board Pins (Jumpered)

Eval Board Signal

RD

J4-3, J4-7

VDRIVE

CS

J4-2, J4-6

DGND

Eval Board Signal

Eval Board Jumper

Position

Notes

SAMPLE

LK1

B

CS

LK2

C

RD

LK3

C

A0

LK 4

C

A1

LK5

C

RES0

LK6

C

There aren’t J4 pins for RES0/1 so have to use jumper pins. It is also possible to hard-wire resolution pins RES0/1, but device tree would need to be changed accordingly.

RES1

LK7

C

There aren’t J4 pins for RES0/1 so have to use jumper pins. It is also possible to hard-wire resolution pins RES0/1, but device tree would need to be changed accordingly.

SOE

LK9

B

VDRIVE

LK703

B

Device Tree

Add dtoverlay=ad2s1210 to /boot/config.txt.

Overlay: ad2s1210-overlay.dts

Sample Images

Eval board connections:

https://wiki.analog.com/_media/resources/tools-software/linux-drivers/iio-resolver/img_20231206_135017785_hdr.jpg

Raspberry Pi connections:

https://wiki.analog.com/_media/resources/tools-software/linux-drivers/iio-resolver/img_20231206_135039086.jpg

Zedboard

https://wiki.analog.com/_media/resources/tools-software/linux-drivers/iio-resolver/img_20231207_080341.jpg

See ad2s1210_sdz for a detailed setup guide

More Information