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The Dragonwing IQ9-EVK contains one low-speed connector (JLS1) that provides access to various GPIOs, CAN, QUPs, and other interfaces.

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Pinout

The figure below shows the default functions of the IQ-9075 EVK 40-pin LS connector.

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GPIOs

The following commands require root privileges. Use sudo su to switch to the root user.

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Identify GPIO Subsystem Numbers

Identify the base GPIO number by running the following command and looking for platform/f000000.pinctrl (gpiochip4). 
mount -t debugfs none /sys/kernel/debug/
cat /sys/kernel/debug/gpio
LS1 Connector GPIO
GPIOOddEvenGPIO
GND12GND
5234CAN_H
5456CAN_L
557832
5391033
44111234
45131435
961516107
951718106
1001920109
992122108
402324105
41252643
422728SAIL59
PME 112930SAIL42
1403132SAIL46
IO EXP3 73334SAIL50
3.3V3536SYS PWR
5V3738SYS PWR
GND3940GND

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Configure GPIOs from User Space

Use the libgpiod library from user space to control the GPIOs for better performance.
1

Install the Arm64 toolchain

sudo apt install gcc-aarch64-linux-gnu
sudo apt install binutils-aarch64-linux-gnu
2

Download and extract libgpiod

wget https://www.kernel.org/pub/software/libs/libgpiod/libgpiod-1.6.4.tar.xz
tar xvf libgpiod-1.6.4.tar.xz
cd libgpiod-1.6.4
3

Configure the sources for static linking

./configure --enable-tools=yes --build x86_64-pc-linux-gnu --host aarch64-linux-gnu CFLAGS="-static -static-libgcc -Wl,-static,--start-group,/usr/lib/gcc-cross/aarch64-linux-gnu/7.5.0/libgcc.a,/usr/lib/gcc-cross/aarch64-linux-gnu/7.5.0/libgcc_eh.a,/usr/aarch64-linux-gnu/lib/libc.a,--end-group"
4

Compile the library

make
Compiling creates linked binaries.
5

Build the statically linked binaries

aarch64-linux-gnu-gcc -static -o tools/gpiodetect tools/gpiodetect.o tools/tools-common.o -Wl,-L<ABSOLUTE_PATH_TO_LIBGPIOD>/libgpiod-1.6.4/lib/.libs,-lgpiod,-lpthread,-static
aarch64-linux-gnu-gcc -static -o tools/gpioget tools/gpioget.o tools/tools-common.o -Wl,-L<ABSOLUTE_PATH_TO_LIBGPIOD>/libgpiod-1.6.4/lib/.libs,-lgpiod,-lpthread,-static
aarch64-linux-gnu-gcc -static -o tools/gpioset tools/gpioset.o tools/tools-common.o -Wl,-L<ABSOLUTE_PATH_TO_LIBGPIOD>/libgpiod-1.6.4/lib/.libs,-lgpiod,-lpthread,-static
aarch64-linux-gnu-gcc -static -o tools/gpiofind tools/gpiofind.o tools/tools-common.o -Wl,-L<ABSOLUTE_PATH_TO_LIBGPIOD>/libgpiod-1.6.4/lib/.libs,-lgpiod,-lpthread,-static
aarch64-linux-gnu-gcc -static -o tools/gpioinfo tools/gpioinfo.o tools/tools-common.o -Wl,-L<ABSOLUTE_PATH_TO_LIBGPIOD>/libgpiod-1.6.4/lib/.libs,-lgpiod,-lpthread,-static
aarch64-linux-gnu-gcc -static -o tools/gpiomon tools/gpiomon.o tools/tools-common.o -Wl,-L<ABSOLUTE_PATH_TO_LIBGPIOD>/libgpiod-1.6.4/lib/.libs,-lgpiod,-lpthread,-static
6

Push the binaries to the device

scp gpiodetect gpioget gpioset gpiofind gpioinfo root@<IP_address>:/path/to/directory/on/device
7

List GPIO chips on the device

Run gpiodetect to list the GPIO chips.
./gpiodetect
Example output:
gpiochip0 [c440000.spmi:pmic@8:pinctrl@c00] (12 lines)
gpiochip1 [c440000.spmi:pmic@1:gpio@8800] (10 lines)
gpiochip2 [c440000.spmi:pmic@2:gpio@8800] (9 lines)
gpiochip3 [c440000.spmi:pmic@0:gpio@b000] (4 lines)
gpiochip4 [f100000.pinctrl] (176 lines)
gpiochip5 [33c0000.pinctrl] (15 lines)
8

Display GPIO line information

Run gpioinfo to view the lines for a specific chip.
./gpioinfo gpiochip4
Example output:
gpiochip4 - 151 lines:
    line   0:      unnamed          "?"   input  active-high [used]
    line   1:      unnamed       unused   input  active-high
    line   2:      unnamed      "perst"  output   active-low [used]
    line   3:      unnamed       unused   input  active-high
    line   4:      unnamed      "perst"  output   active-low [used]
    line   5:      unnamed          "?"   input  active-high [used]
    line   6:      unnamed       unused   input  active-high
    line   7:      unnamed       unused   input  active-high
    line   8:      unnamed       unused   input  active-high
    line   9:      unnamed       unused   input  active-high
    line  10:      unnamed       unused   input  active-high
    line  11:      unnamed       unused   input  active-high
    line  12:      unnamed       unused   input  active-high
    line  13:      unnamed       unused   input  active-high
    line  14:      unnamed       unused   input  active-high
    line  15:      unnamed       unused   input  active-high
......
.....
9

Set a GPIO value

To set GPIO line 54 on gpiochip4, run:
./gpioset gpiochip4 54=1
./gpioinfo gpiochip4 | grep 54
Example output:
gpiochip4 - 176 lines:
   line    54:      unnamed       unused   output  active-high
10

Read a GPIO value

To read GPIO line 0 on gpiochip4, run:
./gpioget gpiochip4 0
Example output:
1
After reading the value, gpioinfo shows the line returned to input mode.
./gpioinfo gpiochip4
Example output:
gpiochip4 - 176 lines:
         line    0:      unnamed       unused   input   active-high
         line    1:      unnamed       unused   input   active-high

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UART

Pins 5 and 7 are configured for UART by default (GPIO lines 54 and 55, mapping to uart12 = qup1_se5 (0xa98000)). Follow the Modify serial engine node procedure to enable the UART interface. After enabling, the device node appears at /dev/ttyHS3. 
#ls -al /dev/ttyHS3
crw-rw---- 1 root dialout 236, 2 Nov 25 18:16 ttyHS3
1

Connect pins

Short pin 5 and pin 7 with a Dupont wire.
Pay attention to pin order. Do not short power and ground pins — this may damage the board.
2

Configure UART

stty -F /dev/ttyHS3 ispeed 115200 ospeed 115200
stty -F /dev/ttyHS3 115200 -echo -icanon -isig -iexten -icrnl -ixon -opost
3

Open two SSH terminals

Terminal 1 (RX):
cat /dev/ttyHS3
Terminal 2 (TX):
su
echo "hello world!" > /dev/ttyHS3

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I2C

I2C (Inter-Integrated Circuit) is a bidirectional 2-wire bus for inter-IC control. Every device on the bus has a unique address. The I2C core supports multi-controller mode, 10-bit target addressing, and 10-bit extendable addressing. Pins 8 and 10 are configured for I2C by default (GPIO lines 32 and 33, mapping to i2c4 = qup0_se4 (0x990000)). Follow the Modify serial engine node procedure to enable the I2C interface. After enabling, verify the device nodes: 
ls /dev/i2c*
# Expected: /dev/i2c-18  /dev/i2c-19  /dev/i2c-20  /dev/i2c-21  /dev/i2c-22  /dev/i2c-23  /dev/i2c-24  /dev/i2c-25
1

push i2c-tools

scp i2cdetect root@<IP address>:/usr
2

List I2C adapters

i2cdetect -l
3

Map adapters to device tree nodes

ls -l /sys/class/i2c-adapter/i2c-*
4

Scan for devices on bus 20

i2cdetect -a -y -r 20
5

Read/write device registers

# Read all registers of device at address 0x38
i2cdump -f -y 1 0x38

# Write 0xaa to register 0x01
i2cset -f -y 1 0x38 0x01 0xaa

# Read register 0x01
i2cget -f -y 1 0x38 0x01

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SPI

SPI (Serial Peripheral Interface) is a synchronous full-duplex 4-wire serial bus. Pins 11 and 13 are configured for SPI by default (GPIO lines 44 and 45, mapping to spi10 = qup1_se3 (0xa8c000)). Follow the Modify serial engine node procedure to enable the SPI interface.