[讨论] [SAM R21]发现R21的ADC稳定性不太好

dcexpert 2015-3-1 22:49 楼主

这几天发现SAM R21的ADC转换不是太稳定，数据波动比较大。测试时将电位器接到ADC6上，使用内部1V基准，转换后发送到串口。

从图中可以看到，数据波动较大，最大991，最小967，波动有24，这还不是波动最大的数据。即使设置ADC采样数据平均，效果也没有任何改善。

参考代码：

/**
* \file
*
* \brief SAM ADC Quick Start
*
* Copyright (C) 2013-2014 Atmel Corporation. All rights reserved.
*
* \asf_license_start
*
* \page License
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The name of Atmel may not be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* 4. This software may only be redistributed and used in connection with an
* Atmel microcontroller product.
*
* THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
* EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* \asf_license_stop
*
*/
/**
* Support and FAQ: visit <a href="http://www.atmel.com/design-support/">Atmel Support</a>
*/
#include <asf.h>
#include <stdio.h>
char str[50];
void configure_adc(void);
//! [module_inst]
struct adc_module adc_instance;
//! [module_inst]
//! [setup]
void configure_adc(void)
{
//! [setup_config]
struct adc_config config_adc;
//! [setup_config]
//! [setup_config_defaults]
adc_get_config_defaults(&config_adc);
//! [setup_config_defaults]
//! [setup_set_config]
adc_init(&adc_instance, ADC, &config_adc);
//! [setup_set_config]
//! [setup_enable]
adc_enable(&adc_instance);
//! [setup_enable]
}
//! [setup]
void configure_usart(void);
//! [module_inst]
struct usart_module usart_instance;
//! [module_inst]
//! [setup]
void configure_usart(void)
{
//! [setup_config]
struct usart_config config_usart;
//! [setup_config]
//! [setup_config_defaults]
usart_get_config_defaults(&config_usart);
//! [setup_config_defaults]
//! [setup_change_config]
config_usart.baudrate = 9600;
config_usart.mux_setting = EDBG_CDC_SERCOM_MUX_SETTING;
config_usart.pinmux_pad0 = EDBG_CDC_SERCOM_PINMUX_PAD0;
config_usart.pinmux_pad1 = EDBG_CDC_SERCOM_PINMUX_PAD1;
config_usart.pinmux_pad2 = EDBG_CDC_SERCOM_PINMUX_PAD2;
config_usart.pinmux_pad3 = EDBG_CDC_SERCOM_PINMUX_PAD3;
//! [setup_change_config]
//! [setup_set_config]
while (usart_init(&usart_instance,
EDBG_CDC_MODULE, &config_usart) != STATUS_OK) {
}
//! [setup_set_config]
//! [setup_enable]
usart_enable(&usart_instance);
//! [setup_enable]
}
//! [setup]
int main(void)
{
system_init();
//! [setup_init]
delay_init();
configure_adc();
configure_usart();
//! [setup_init]
//! [main]
//! [get_res]
uint16_t result;
while(1)
{
//! [start_conv]
adc_start_conversion(&adc_instance);
//! [start_conv]
do {
/* Wait for conversion to be done and read out result */
} while (adc_read(&adc_instance, &result) == STATUS_BUSY);
sprintf(str, "%d\r\n", result);
usart_write_buffer_wait(&usart_instance, str, sizeof(str));
delay_ms(500);
//! [get_res]
}
//! [inf_loop]
while (1) {
/* Infinite loop */
}
//! [inf_loop]
//! [main]
}