Работа с GPIO/en: различия между версиями

Работа с GPIO/en (просмотреть исходный код)

Версия 19:31, 24 апреля 2019

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In Wiren Board part GPIO output to terminal blocks, connectors on the expansion modules, the other part is used for business purposes.
In Wiren Board a part of GPIOs is output to terminal blocks,a part - to connectors on the expansion modules, the other part is used for utility purposes.
GPIO are also used to control the switching transistors for low-voltage load.  
GPIO are also used to control the switching transistors for low-voltage load.  


The correspondence between numbers GPIO Linux and their location and function can be found in the table [[WB SH 3.5: Список GPIO| WB SH 3.5: List of GPIO]] or [[WB rev. 2.8: Список GPIO| WB rev. 2.8: List of GPIO]].
The correspondence between GPIO numbers in Linux and between their location and function can be found in the table [[WB SH 3.5: Список GPIO| WB SH 3.5: List of GPIO]] or [[WB rev. 2.8: Список GPIO| WB rev. 2.8: List of GPIO]].


In Wiren Board rev. 2.8 8 GPIO on a special connector connected via [[Special: MyLanguage / MCP23S08 | MCP23S08]] and temporarily do not work with standard Linux API. How to work with them there on the page[[Special:MyLanguage/MCP23S08|MCP23S08]].
In Wiren Board rev. 2.8 8 GPIO are placed on a special connector and connected via [[Special:MyLanguage/MCP23S08|MCP23S08]] and temporarily do not work with Linux API standard. How to work with them: see page [[Special:MyLanguage/MCP23S08|MCP23S08]].


<b> All GPIO (as well as other ports Wiren Board) working with voltage 3.3V. In no case do not connect directly to the GPIO signals with voltage over 3.3V! In case you want to connect devices operating at a higher voltage, you must use matching circuits or connected (for 5V) through a resistor of 20 kOhm or more</b>
<b> All GPIOs (as well as other ports of Wiren Board controllers) work with 3.3V voltage.Do not connect signals with voltage over 3.3V directly to the GPIO! In case you want to connect devices operating at a higher voltage, you must use matching circuits or connect(for 5V) via a resistor of 20 kOhm or more</b>




On some GPIO (particularly at the 3 GPIO, launched into terminals in Wiren Board rev. 2.8) can be programmatically set to lift 47K + 3.3V. See. [[Special: MyLanguage / Pin_pull-up | Pin_pull-up]].
On some GPIOs (particularly at the 3 GPIOs, launched into terminals in Wiren Board rev. 2.8) can be programmatically set to lift 47K + 3.3V. See. [[Special:MyLanguage/Pin_pull-up|Pin_pull-up]].




=== sysfs interface under Linux ===
=== sysfs interface in Linux ===


GPIO under Linux are supported through sysfs-interface.
GPIOs in Linux are supported through sysfs-interface.


To work through a certain GPIO sysfs it must be exported:
To work via sysfs a certain GPIO must be exported:


Here and further N - number of gpio
Here and further N is a number of gpio


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В директории <b>/sys/class/gpioN</b> теперь находятся файлы для работы с GPIO (где N - номер GPIO, как и было сказано ранее):
The folder <b>/sys/class/gpioN</b> now contains files to work with GPIO (where N is a GPIO number):
The directory <b>/sys/class/gpioN</b> are now files to work with GPIO (where N - No. of GPIO, as was said earlier):


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echo in > /sys/class/gpio/gpioN/direction #set the GPIO to input
echo in > /sys/class/gpio/gpioN/direction #set the GPIO N to input
echo out > /sys/class/gpio/gpioN/direction # set the GPIO to output  
echo out > /sys/class/gpio/gpioN/direction # set the GPIO N to output  
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Reading and Setting the GPIO is made using the file <b>value</b>.  
Reading and setting the GPIO is made using the file <b>value</b>.  


Reading:
Reading:
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Interrupts can be caught from userspace using the system call poll () and select () on file value.
Interrupts can be caught from userspace using the system call epoll () and select () on file value.
Example of look here [https://github.com/contactless/wiegand-linux-sysfs]
See example here [https://github.com/contactless/wiegand-linux-sysfs]


see also [http://elinux.org/GPIO elinux.org]
see also [http://elinux.org/GPIO elinux.org]
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===Direct access by processor memory===
===Direct access by processor memory===


<b>This method is strongly NOT recommended for use without sufficient reason. To work in C / C ++ is to use the files to work through sysfs, as described in the previous section</b>.
<b>This method is NOT strongly recommended for use without sufficient reason. To work in C / C ++ is to use the files to work through sysfs, as described in the previous section</b>.


Driving GPIO can use the direct access to the processor registers, bypassing the Linux interface/dev/mem. At the same time, compared to the work via sysfs minimization of costs. This method can be used,
You can manage GPIO using the direct access to the processor registers, bypassing the Linux interface/dev/mem. At the same time, compared to the work via sysfs, this case minimizes costs. This method can be used,
if you need a very fast access to GPIO, such bitbang protocols or PWM. It should be borne in mind that the process scheduler can still contribute to the work program of significant delays.
if you need a very fast access to GPIO, such bitbang protocols or PWM. It should be borne in mind that the process scheduler can still contribute to the work program of significant delays.
It is recommended to make time-critical tasks in the kernel.
It is recommended to make time-critical tasks in the kernel.
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===GPIO and Device Tree===
===GPIO and Device Tree===


Pointing to the GPIO Device Tree you need to configure the GPIO to work in a mode of software SPI, I2C, GPIO to be used as the source of the interrupt, etc.
It's necessary to place the GPIO in Device Tree to configure the GPIO to work in a mode of software SPI, I2C, for GPIO to be used as the source of the interrupt, etc.
For example on a pin 10 @ UEXT1 (CS) and pins 5 @ UEXT2 (SCL), 6 @ UEXT2 (SDA), 10 @ UEXT2 (CS) derived processor GPIO lines. They can be configured to use such as a chip-select for as SPI or I2C.
For example on a pin 10 @ UEXT1 (CS) and pins 5 @ UEXT2 (SCL), 6 @ UEXT2 (SDA), 10 @ UEXT2 (CS) GPIO processor lines are derived. They can be configured to use such as a chip-select for SPI or as I2C.


GPIO процессора и периферийных устройств разбиты на банки (gpiochip). GPIO процессора разбиты на 3 банка по 32 GPIO: gpio0, gpio1, gpio2. Адресация GPIO в Device Tree происходит по номеру банка и номеру GPIO *внутри* банка.
The processor's and peripherals' GPIOs are divided into banks (gpio chip).Processor's  GPIO are split into 3 banks for 32 GPIO: gpio0, gpio1, gpio2. Addressing GPIO in Device Tree comes to the number of the bank and the number of GPIO * in * the bank.




====Пример 1====
====Example 1====


Определим сигнал 6@UEXT2 (SDA) в качестве источника прерываний для драйвера mrf24j40. Согласно таблице [[Special:MyLanguage/Список GPIO|Список GPIO]], сигнал соответствует GPIO 53 процессора. 53 принадлежит второму банку gpio (от 32 до 63). Номер GPIO внутри банка 53-32=21 :
We define signal 6 @ UEXT2 (SDA) as the source of the interrupt driver mrf24j40. According to the table [[Special:MyLanguage/Список_GPIO/en|List of GPIOs]], signal corresponds to 53 GPIO of processor. 53 belongs to the second bank gpio (32 to 63). GPIO number inside the bank 53-32 = 21:


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RomanKulibaba
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Источник — https://wirenboard.com/wiki/Служебная:Сравнение_версий/7444...18919