ADC Device Driver

This document describes use of the generic ADC device driver in Nano-RK. For a running example please refer to the basic_adc project.

Adding the Driver to a Project

When adding the sensor driver to a project make sure to do the following:

  • Update NRK_MAX_DRIVER_CNT in nrk_cfg.h
  • Add the driver source to the local makefile
    • SRC += $(ROOT_DIR)/src/drivers/platform/$(PLATFORM_TYPE)/source/adc_driver.c
  • Register the driver before nrk_start() is called 
    •   // Register the ADC device driver
  val=nrk_register_driver( &dev_manager_adc,ADC_DEV_MANAGER);
  if(val==NRK_ERROR) nrk_kprintf( PSTR("Failed to load my ADC driver\r\n") );
  • Make sure ADC_DEV_MANAGER is uniquely defined in /src/drivers/include/nrk_driver_list.h
  • Make sure to add the following includes to your source
    • #include <nrk_driver_list.h>
    • #include <nrk_driver.h>
    • #include <adc_driver.h>

Opening the Device

The following sample of code will open an instance of the driver. This will initialize the ADC on the processor. 

int8_t fd;
...
fd=nrk_open(ADC_DEV_MANAGER,READ);
        if(fd==NRK_ERROR) nrk_kprintf(PSTR("Failed to open adc driver\r\n"));

Selecting an ADC Channel

Using nrk_set_status( device, value, key) allows the application to configure which sensor value will be read by the nrk_read() command. device is the descriptor returned by nrk_open(). value is the command parameter you wish to set, in this case ADC_CHAN. key is the value of the channel you wish to select and can take the following values:

  • uint8_t with value 0-7
  • CHAN_0
  • CHAN_1
  • CHAN_2
  • CHAN_3
  • CHAN_4
  • CHAN_5
  • CHAN_6
  • CHAN_7 
val=nrk_set_status(fd,ADC_CHAN,5);

Reading the ADC

After a channel has been selected, the value can be read using the nrk_read(device,uint8_t *buf, uint8_t size) function. device is the device file descriptor returned by nrk_open(). buf is a pointer to the memory where the driver will write the value. size is the max size of the buffer (in this case 1 byte). Below is an example of reading the adc: 

uint8_t buf;
...
val=nrk_read(fd,&buf,1);
printf( "ADC value=%d",buf);

Closing the Device

Closing the device is potentially important for saving on power and allowing multiple tasks to access the resource. 

nrk_close(fd);