SAR使用参考

version 1.0

1. 概述¶

目前SAR口的ADC精度是10bit。

本篇文主要介绍sar口如何配置以及如何在用户层使用sar口。

2. Kernel配置¶

2.1. Kernel config中打开CONFIG_MS_SAR¶

图2-1

配置完成后，重新编译kernel，替换kernel image到project烧录

2.2. Padmux中将对应的pin配置成sar mode¶

图2-2

3. SAR控制¶

3.1. SAR控制概述¶

SAR驱动程序为用户提供ioctl接口，用以初始化SAR并获取 SAR_ADC值。

3.2. Using SAR in user space¶

3.2.1. SAR device¶

"/dev/sar”

3.2.2. Include file¶

mdrv_sar_io.h

3.2.3. SAR IOCTL Commands¶

IOCTL command	Parameter	Description
IOCTL_SAR_INIT	NULL	initialize
IOCTL_SAR_SET_CHANNEL_READ_VALUE	typedef struct { int channel_value; //[IN] int adc_value; //[OUT] } SAR_ADC_CONFIG_READ; channel_value: sar channel number(possible value: 0 or 1) adc_value: sar adc value	Get sar adc value

3.2.4. Example¶

#include <stdio.h>

#include<sys/types.h>

#include<sys/stat.h>

#include<fcntl.h>

#include<errno.h>

#include <sys/ioctl.h>

#include "mdrv_sar_io.h"

int main(void)
{
    int i;

    SAR_ADC_CONFIG_READ  adcCfg;

    adcCfg.channel_value = 0;   //注意：PAD_SAR_GPIO0 = 0 PAD_SAR_GPIO1 = 1 PAD_SAR_GPIO2 = 2

    int fd = open("/dev/sar", O_WRONLY);

    if(fd == -1) {

        int err = errno;

        printf("\n!!! FAILED to open /dev/sar, errno: %d %s\n", err, strerror(err));
        return -1;
    }

    if (ioctl(fd, IOCTL_SAR_INIT, NULL) < 0) {

        int err = errno;

        printf("\n!!! IOCTL_SAR_INIT FAILED, errno: %d, %s\n", err, strerror(err));
    }

    for (i=0; i < 100; i++)

    {

        if (ioctl(fd, IOCTL_SAR_SET_CHANNEL_READ_VALUE, &adcCfg) < 0) {

            int err = errno;

            printf("\n!!! IOCTL_SAR_SET_CHANNEL_READ_VALUE FAILED, errno: %d, %s\n", err, strerror(err));

        }

        else {

            printf("SAR: get value %d", adcCfg.adc_value);

        }

        usleep(100000);

    }

}