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| <!-- Set release according to "release" parameter in URL and use RELEASE_SUMO_V1.0_VAR-SOM-MX8X as default
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| --> {{#vardefine:RELEASE_PARAM|{{#urlget:release}}}} <!--
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| --> {{#lst:Yocto_Platform_Customization|{{#var:RELEASE_PARAM|RELEASE_SUMO_V1.0_VAR-SOM-MX8X}}}} <!--
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| --> {{PageHeader|{{#var:HARDWARE_NAME}} GPIO}} {{DocImage|category1=Yocto|category2={{#var:HARDWARE_NAME}}}} __toc__
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|
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| = GPIO state =
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| The current state of the system's GPIOs can be obtained in user-mode, as shown in the following example:
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| {{#ifeq: {{#var:HARDWARE_NAME}} | VAR-SOM-MX8X |
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| <pre>
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| # cat /sys/kernel/debug/gpio
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| gpiochip0: GPIOs 0-31, parent: platform/5d080000.gpio, 5d080000.gpio:
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| gpio-12 ( |ov5640_mipi_reset ) out hi
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| gpio-16 ( |fsl_lpspi ) in hi
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| gpio-26 ( |ov5640_mipi_pwdn ) out lo
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|
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| gpiochip1: GPIOs 32-63, parent: platform/5d090000.gpio, 5d090000.gpio:
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| gpio-32 ( |fsl_lpspi ) in hi
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| gpio-34 ( |phy-reset ) out hi
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| gpio-39 ( |reg_sd_pwr ) out hi
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| gpio-60 ( |reg_ethphy0 ) out hi
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|
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| gpiochip2: GPIOs 64-95, parent: platform/5d0a0000.gpio, 5d0a0000.gpio:
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|
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| gpiochip3: GPIOs 96-127, parent: platform/5d0b0000.gpio, 5d0b0000.gpio:
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| gpio-120 ( |cam_buf_en ) out hi
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|
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| gpiochip4: GPIOs 128-159, parent: platform/5d0c0000.gpio, 5d0c0000.gpio:
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| gpio-149 ( |usb_otg1_vbus ) out hi
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| gpio-150 ( |cd ) in lo IRQ
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|
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| gpiochip5: GPIOs 160-191, parent: platform/5d0d0000.gpio, 5d0d0000.gpio:
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| gpio-169 ( |connect ) in hi IRQ
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|
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| gpiochip6: GPIOs 192-223, parent: platform/5d0e0000.gpio, 5d0e0000.gpio:
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|
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| gpiochip7: GPIOs 224-255, parent: platform/5d0f0000.gpio, 5d0f0000.gpio:
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|
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| gpiochip8: GPIOs 504-511, parent: i2c/1-0020, pca9534, can sleep:
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| gpio-504 ( |heartbeat ) out lo
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| gpio-505 ( |Back ) in hi IRQ
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| gpio-506 ( |Home ) in hi IRQ
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| gpio-507 ( |Menu ) in hi IRQ
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| gpio-508 ( |usb3_sel ) out lo
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| gpio-509 ( |phy-reset ) out hi
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| gpio-510 ( |reg_vselect ) out hi
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| gpio-511 ( |reg_ethphy1 ) out hi
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| </pre>
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| <pre>
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| # cat /sys/kernel/debug/gpio
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| gpiochip0: GPIOs 0-31, parent: platform/5d080000.gpio, 5d080000.gpio:
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| gpio-14 ( |cd ) in lo IRQ
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| gpio-18 ( |usb_otg1_vbus ) out hi
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| gpio-22 ( |cam_buf_en ) out hi
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| gpio-30 ( |sysfs ) out hi
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|
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| gpiochip1: GPIOs 32-63, parent: platform/5d090000.gpio, 5d090000.gpio:
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| gpio-54 ( |hdmi_i2c_signal_rout) out lo
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|
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| gpiochip2: GPIOs 64-95, parent: platform/5d0a0000.gpio, 5d0a0000.gpio:
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| gpio-77 ( |ads7846_pendown ) in hi IRQ
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| gpio-92 ( |phy-reset ) out hi
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|
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| gpiochip3: GPIOs 96-127, parent: platform/5d0b0000.gpio, 5d0b0000.gpio:
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| gpio-100 ( |ov5640_mipi_pwdn ) out lo
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| gpio-102 ( |ov5640_mipi_reset ) out hi
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| gpio-106 ( |fsl_lpspi ) out hi
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| gpio-107 ( |connect ) in hi IRQ
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| gpio-120 ( |fsl_lpspi ) in hi
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|
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| gpiochip4: GPIOs 128-159, parent: platform/5d0c0000.gpio, 5d0c0000.gpio:
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| gpio-154 ( |sysfs ) out lo
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|
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| gpiochip5: GPIOs 160-191, parent: platform/5d0d0000.gpio, 5d0d0000.gpio:
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|
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| gpiochip6: GPIOs 192-223, parent: platform/5d0e0000.gpio, 5d0e0000.gpio:
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|
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| gpiochip7: GPIOs 224-255, parent: platform/5d0f0000.gpio, 5d0f0000.gpio:
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|
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| gpiochip8: GPIOs 504-511, parent: i2c/1-0020, pca9534, can sleep:
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| gpio-504 ( |heartbeat ) out hi
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| gpio-505 ( |Back ) in hi IRQ
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| gpio-506 ( |Home ) in hi IRQ
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| gpio-507 ( |Menu ) in hi IRQ
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| gpio-508 ( |usb3_signal_route ) out lo
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| gpio-509 ( |phy-reset ) out hi
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| gpio-510 ( |reg_vselect ) out hi
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| gpio-511 ( |reg_ethphy1 ) out hi
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| </pre>
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| }}
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|
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| Each GPIO is defined as in or out and the state is shown as lo or hi.<br>
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| For example pin {{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX8X|150|44}} is the SD card card-detect.
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| When an SD card is plugged in, the state will be:
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|
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| gpio-{{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX8X|150|44}} ( |cd ) in lo IRQ
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|
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| When the SD card is removed, the state will be:
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|
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| gpio-{{#ifeq: {{#var:HARDWARE_NAME}}|VAR-SOM-MX8X|150|44}} ( |cd ) in hi IRQ
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|
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| = Manipulating a single GPIO via /sys/class/gpio =
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| == Using a command line or a script ==
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| GPIOs in i.MX are grouped in groups of 32 pins.<br>
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| For example, GPIO0_3 belongs to the first group, pin 3. Its absolute number will be 3.<br>
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| GPIO4_21 will be 4*32+21=149.<br>
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| Assuming this GPIO is defined in your device tree, the following is an example of how to use it from userspace.<br>
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| <br>
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| To export the GPIO for userspace use:
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| <pre>
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| # echo 149 > /sys/class/gpio/export
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| </pre>
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| <br>
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| To configure as output:
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| <pre>
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| # echo out > /sys/class/gpio/gpio149/direction
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| </pre>
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| Set GPIO high:
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| <pre>
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| # echo 1 > /sys/class/gpio/gpio149/value
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| </pre>
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| Set GPIO low:
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| <pre>
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| # echo 0 > /sys/class/gpio/gpio149/value
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| </pre>
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| <br>
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| To configure as input:
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| <pre>
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| # echo in > /sys/class/gpio/gpio149/direction
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| </pre>
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| Read the current value:
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| <pre>
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| # cat /sys/class/gpio/gpio149/value
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| </pre>
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| <br>
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| To free the GPIO after you're done using it:
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| <pre>
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| # echo 149 > /sys/class/gpio/unexport
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| </pre>
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|
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| == Using a C application ==
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| All of the command line operations above can be translated to C code:<br>
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| Reserve (export) the GPIO:<br>
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| <pre>
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| #define IMX_GPIO_NR(port, index) ((port)*32)+((index)&31))
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|
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| int fd;
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| char buf[MAX_BUF];
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| int gpio = IMX_GPIO_NR(4, 21); /* Just an example */
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|
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| fd = open("/sys/class/gpio/export", O_WRONLY);
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|
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| sprintf(buf, "%d", gpio);
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|
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| write(fd, buf, strlen(buf));
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|
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| close(fd);
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| </pre>
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| Set the GPIO direction:<br>
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| <pre>
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| sprintf(buf, "/sys/class/gpio/gpio%d/direction", gpio);
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|
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| fd = open(buf, O_WRONLY);
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|
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| /* Set out direction */
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| write(fd, "out", 3);
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| /* Set in direction */
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| write(fd, "in", 2);
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|
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| close(fd);
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| </pre>
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|
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| In case of out direction set the GPIO value:
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| <pre>
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| sprintf(buf, "/sys/class/gpio/gpio%d/value", gpio);
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|
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| fd = open(buf, O_WRONLY);
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|
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| /* Set GPIO high status */
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| write(fd, "1", 1);
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| /* Set GPIO low status */
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| write(fd, "0", 1);
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|
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| close(fd);
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| </pre>
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|
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| In case of in direction get the current GPIO value:
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| <pre>
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| char value;
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|
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| sprintf(buf, "/sys/class/gpio/gpio%d/value", gpio);
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|
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| fd = open(buf, O_RDONLY);
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|
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| read(fd, &value, 1);
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|
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| if (value == '0') {
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| /* Current GPIO status low */
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| } else {
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| /* Current GPIO status high */
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| }
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|
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| close(fd);
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| </pre>
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|
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| Once finished, free (unexport) the GPIO:
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| <pre>
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| fd = open("/sys/class/gpio/unexport", O_WRONLY);
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|
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| sprintf(buf, "%d", gpio);
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|
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| write(fd, buf, strlen(buf));
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|
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| close(fd);
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| </pre>
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|
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| Important notes:<br>
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| * Remember that after the first read operation, the file pointer will move to the next position in the file, so to get a correct value for each read operation you simply have to set the file pointer at the beginning of the file before reading by using the following command:
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| <pre>
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| lseek(fd, 0, SEEK_SET);
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| </pre>
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| * This is only a short example. If you want to use it in your code, remember to add error handling to it.
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