GPIO Usage Guidelines

• How to Use
• Determining a GPIO Pin Number
• Using APIs to Operate GPIO Pins

How to Use

The GPIO APIs use the GPIO pin number to specify a pin. Figure 1 shows the general process of using a GPIO.

Figure 1 Process of using a GPIO

Determining a GPIO Pin Number

The method for converting GPIO pin numbers varies according to the GPIO controller model, parameters, and controller driver of different system on chips (SoCs).

• Hi3516D V300

  A controller manages 12 groups of GPIO pins. Each group contains 8 GPIO pins.

  GPIO pin number = GPIO group index (0-11) x Number of GPIO pins in each group (8) + Offset in the group

  Example: GPIO number of GPIO10_3 = 10 x 8 + 3 = 83

• Hi3518E V300

  A controller manages 10 groups of GPIO pins. Each group contains 10 GPIO pins.

  GPIO pin number = GPIO group index (0–9) x Number of GPIO pins in each group (10) + Offset in the group

  Example: GPIO pin number of GPIO7_3 = 7 x 10 + 3 = 73

Using APIs to Operate GPIO Pins

• Set the direction for a GPIO pin.

  Before performing read/write operations on a GPIO pin, call the following function to set the direction:

  int32_t GpioSetDir(uint16_t gpio, uint16_t dir);

  Table 1 Description of GpioSetDir

  Parameter	Description
  gpio	GPIO pin number.
  dir	Direction to set.
  Return Value	Description
  0	The setting is successful.
  Negative value	The setting failed.

• Read or write the level value for a GPIO pin.

  To read the level value of a GPIO pin, call the following function:

  int32_t GpioRead(uint16_t gpio, uint16_t *val);

  Table 2 Description of GpioRead

  Parameter	Description
  gpio	GPIO pin number.
  val	Pointer to the level value.
  Return Value	Description
  0	Succeeded in reading the level value.
  Negative value	Failed to read the level value.

  To write the level value for a GPIO pin, call the following function:

  int32_t GpioWrite(uint16_t gpio, uint16_t val);

  Table 3 Description of GpioWrite

  Parameter	Description
  gpio	GPIO pin number.
  val	Level value to write.
  Return Value	Description
  0	Succeeded in writing the level value.
  Negative value	Failed to write the level value.

  Example:

  int32_t ret;
  uint16_t val;
  /* Set the output direction for GPIO3. */
  ret = GpioSetDir(3, GPIO_DIR_OUT);
  if (ret != 0) {
      HDF_LOGE("GpioSerDir: failed, ret %d\n", ret);
      return;
  }
  /* Write the low level GPIO_VAL_LOW for GPIO3. */
  ret = GpioWrite(3, GPIO_VAL_LOW);
  if (ret != 0) {
      HDF_LOGE("GpioWrite: failed, ret %d\n", ret);
      return;
  }
  /* Set the input direction for GPIO6. */
  ret = GpioSetDir(6, GPIO_DIR_IN);
  if (ret != 0) {
      HDF_LOGE("GpioSetDir: failed, ret %d\n", ret);
      return;
  }
  /* Read the level value of GPIO6. */
  ret = GpioRead(6, &val);

• Set the ISR function for a GPIO pin.

  To set the ISR function for a GPIO pin, call the following function:

  int32_t GpioSetIrq(uint16_t gpio, uint16_t mode, GpioIrqFunc func, void *arg);

  Table 4 Description of GpioSetIrq

  Parameter	Description
  gpio	GPIO pin number.
  mode	Interrupt trigger mode.
  func	ISR function to set.
  arg	Pointer to the parameters passed to the ISR function.
  Return Value	Description
  0	The setting is successful.
  Negative value	The setting failed.

  CAUTION: Only one ISR function can be set for a GPIO pin at a time. If GpioSetIrq is called repeatedly, the previous IRS function will be replaced.

  If the ISR function is no longer required, call the following function to cancel the setting:

  int32_t GpioUnSetIrq(uint16_t gpio);

  Table 5 Description of GpioUnSetIrq

  Parameter	Description
  gpio	GPIO pin number.
  Return Value	Description
  0	The ISR function is canceled.
  Negative value	Failed to cancel the ISR function.

  After the ISR function is set, call the following function to enable a GPIO interrupt:

  int32_t GpioEnableIrq(uint16_t gpio);

  Table 6 Description of GpioEnableIrq

  Parameter	Description
  gpio	GPIO pin number.
  Return Value	Description
  0	The GPIO interrupt is enabled.
  Negative value	Failed to enable a GPIO interrupt.

  CAUTION: The configured ISR function can be responded only after the ISR function is enabled.

  Use the following function to disable the GPIO interrupt:

  int32_t GpioDisableIrq(uint16_t gpio);

  Table 7 Description of GpioDisableIrq

  Parameter	Description
  gpio	GPIO pin number.
  Return Value	Description
  0	The GPIO interrupt is disabled.
  Negative value	Failed to disable the GPIO interrupt.

  Example:

  /* ISR function */
  */
  int32_t MyCallBackFunc(uint16_t gpio, void *data)
  {
      HDF_LOGI("%s: gpio:%u interrupt service in! data=%p\n", __func__, gpio, data);
      return 0;
  }
  
  int32_t ret;
  /* Set the ISR function to MyCallBackFunc, the parameter to NULL, and the interrupt trigger mode to rising edge. */
  ret = GpioSetIrq(3, OSAL_IRQF_TRIGGER_RISING, MyCallBackFunc, NULL);
  if (ret != 0) {
      HDF_LOGE("GpioSetIrq: failed, ret %d\n", ret);
      return;
  }
  
  /* Enable an interrupt for GPIO3. */
  ret = GpioEnableIrq(3);
  if (ret != 0) {
      HDF_LOGE("GpioEnableIrq: failed, ret %d\n", ret);
      return;
  }
  
  /* Disable the interrupt for GPIO3. */
  ret = GpioDisableIrq(3);
  if (ret != 0) {
      HDF_LOGE("GpioDisableIrq: failed, ret %d\n", ret);
      return;
  }
  
  /* Cancel the ISR function for GPIO3. */
  ret = GpioUnSetIrq(3);
  if (ret != 0) {
      HDF_LOGE("GpioUnSetIrq: failed, ret %d\n", ret);
      return;
  }