IIO (Industrial I / O) es un subsistema del kernel de Linux para convertidores de analógico a digital (ADC), convertidores de digital a analógico (DAC) y varios tipos de sensores. Puede utilizarse en dispositivos industriales de alta velocidad. También incluye una API incorporada para otros controladores.

Industrial I/O Linux ( ) , . , sysfs devfs.

IIO:

IIO :

(: )
- , DFSDM (, , )
, TIM LPTIM
SPI I2C

IIO , , ...

IIO

/ :

# https://www.kernel.org/doc/Documentation/i2c/dev-interface
open("/dev/i2c-1", O_RDWR);
# https://www.kernel.org/doc/Documentation/spi/spidev.rst
open("/dev/spidev2.0", O_RDWR);

, :

— ?

"" ( ).

IIO - , - poll .

IIO — .

IIO

sysfs ( ):

# cat /sys/bus/iio/devices/iio\:device0/in_accel_x_raw
-493

"" , .

read():

#      
(cd /sys/bus/iio/devices/iio:device0/scan_elements/ && for file in *_en; do echo 1 > $file; done)

int fd = open("/dev/iio:device0");
read(fd, buffer, scan_size);
#  scan_size      ,     1  /sys/bus/iio/devices/iio:device0/scan_elements/*_en

scan_size, "" , , .

IIO struct iio_chan_spec:

IIO types

BME280

/* https://elixir.bootlin.com/linux/v5.9-rc1/source/drivers/iio/pressure/bmp280-core.c#L132*/
static const struct iio_chan_spec bmp280_channels[] = {
    {
        .type = IIO_PRESSURE,
        .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
                      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
    },
    {
        .type = IIO_TEMP,
        .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
                      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
    },
    {
        .type = IIO_HUMIDITYRELATIVE,
        .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
                      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
    },
};

, , — .

Linux , .

, kfifo .

, , , .

. , , , , , .

, CLOCK_REALTIME.

IIO Triggered Buffers

"" , user space.

, .

# cat /sys/bus/iio/devices/iio\:device0/trigger/current_trigger
icm20608-dev0
# echo > /sys/bus/iio/devices/iio\:device0/trigger/current_trigger
# cat /sys/bus/iio/devices/iio\:device0/trigger/current_trigger
# echo "icm20608-dev0" > /sys/bus/iio/devices/iio\:device0/trigger/current_trigger

Official Trigger Documentation

IIO sysfs trigger

Industrial IIO configfs support

Triggered buffer support trigger buffer support for IIO subsystem of Linux device driver

Device owned triggers

, device tree:

icm20608: imu@0 {
    ...
    interrupt-parent = <&gpio5>;
    interrupts = <11 IRQ_TYPE_EDGE_RISING>;
    ...
};

cat /sys/bus/iio/devices/trigger0/name
icm20608-dev0

gpio, , .

Interrupt triggers (also known as gpio trigger)

iio-trig-interrupt

, . gpio, .

, maintainer'a IIO Jonathan Cameron, .

— Triggered buffer support trigger buffer support for IIO subsystem of Linux device driver

.

[v3,1/6] dt-bindings: iio: introduce trigger providers, consumers

device tree :

trig0: interrupt-trigger0 {
    #io-trigger-cells = <0>;
    compatible = "interrupt-trigger";
    interrupts = <11 0>;
    interrupt-parent = <&gpioa>;
};

sysfs trigger

iio-trig-sysfs

sysfs — , .

# echo 10 > /sys/bus/iio/devices/iio_sysfs_trigger/add_trigger

"sysfstrig%d", .

High resolution timer trigger

1 .

# mkdir /sys/kernel/config/iio/triggers/hrtimer/my_trigger_name
# cat /sys/bus/iio/devices/trigger4/name
my_trigger_name
# cat /sys/bus/iio/devices/trigger4/sampling_frequency
100

— "" SoC.

loop trigger

iio-trig-loop

PATCH v1 5/5 iio:pressure:ms5611: continuous sampling support

.

. :

iio:trigger: Experimental kthread tight loop trigger.

DT, , .

Device tree

label , , of_node iio:device — /sys/bus/iio/devices/iio\:device0/of_node/.

— https://elixir.bootlin.com/linux/v5.9-rc1/source/Documentation/devicetree/bindings/iio

, IIO, enum iio_chan_type . iio_event_monitor.

IIO iio-buffer-sysfs-interface.

[be|le]:[s|u]bits/storagebitsXrepeat[>>shift]

icm20608:

# cat /sys/bus/iio/devices/iio\:device0/scan_elements/*_type
be:s16/16>>0
be:s16/16>>0
be:s16/16>>0
be:s16/16>>0
be:s16/16>>0
be:s16/16>>0
le:s64/64>>0

le be c
— , s u
/ ,

be:u4/8>>0
be:u4/8>>4

repeat — 1 .

Scaling and offset

/sys/bus/iio/devices/iio:deviceX/in_*_raw
/sys/bus/iio/devices/iio:deviceX/in_*_offset
/sys/bus/iio/devices/iio:deviceX/in_*_scale

(raw + offset)*scale, offset'a .

How to do a simple ADC conversion using the sysfs interface

iio_simple_dummy

iio_simple_dummy — IIO :

IIO_VOLTAGE
IIO_ACCEL
IIO_ACTIVITY

The iio_simple_dummy Anatomy

iio_simple_dummy

libiio

— libiio Analog Devices.

, / .

/, , Linux, Windows Mac , USB, Ethernet Serial.

iiod:

On remote :

host # iiod

On local :

local $ iio_info -n [host_address]
local $ iio_attr -u ip:[host_address] -d
local $ iio_readdev -u ip:[host_address] -b 256 -s 0 icm20608

Matlab, .

, libiio .

https://github.com/maquefel/icm20608-iio

libiio

sysfs , :

, /sys/bus/iio/iio:deviceN/name, /sys/bus/iio/iio:deviceN /dev/iio:deviceN
/sys/bus/iio/iio:deviceN/scan_elements/, , *_en
/sys/bus/iio/iio:deviceN/enable

E libiio.

https://elixir.bootlin.com/linux/v5.9-rc1/source/drivers/iio/industrialio-buffer.c#L574

    # bytes -      
    # length -    
    # offset -        
    if (bytes % length == 0)
        offset = bytes;
    else
        offset = bytes - bytes % length + length;

    bytes = offset + length;

libiio, :

, (Sign extension)
offset,
scale,

    input = is_be ? betoh(input) : letoh(input);
    input >>= shift;
    input &= BIT_MASK(bits);
    value = is_signed ? (float)sext(input, bits) : (float)input;
    if(with_offset) value += offset;
    if(with_scale) value *= scale;

: (Sign extension) . SignExtend.

libiio

libiio-loop.c

.

#    uri
# uri = "ip:127.0.0.1"
# uri = "local:"
# uri = "usb:"
ctx = iio_create_context_from_uri(uri);

#  
#  device = icm20608
dev = iio_context_find_device(ctx, device);

#   
nb_channels = iio_device_get_channels_count(dev);

#   
for(int i = 0; i < nb_channels; i++)
    iio_channel_enable(iio_device_get_channel(dev, i));

# buffer_size = SAMPLES_PER_READ,    (  )
buffer = iio_device_create_buffer(dev, buffer_size, false);

#    
iio_buffer_set_blocking_mode(buffer, true);

while(true) {
    #  
    iio_buffer_refill(buffer);

    #   -      libiio
    #     "" ,        
    #    
    # ssize_t print_sample(const struct iio_channel *chn, void *buffer, size_t bytes, __notused void *d)
    # const struct iio_channel *chn -     
    # void *buffer -        
    # size_t bytes -    
    # __notused void *d -         iio_buffer_foreach_sample
    iio_buffer_foreach_sample(buffer, print_sample, NULL);
}

#  
iio_buffer_destroy(buffer);

#  
iio_context_destroy(ctx);