CooCox ADC learning notes

*** ADC CoX Peripheral Library Analog-to-Digital Converter (ADC) Peripheral Driver. ***

http://www.coocox.org/cox/manual/interface/group___a_d_c.html

Collaboration diagram for ADC:

Modules

  xADC
 
CoX ADC Peripheral Interface.


Detailed Description

Analog-to-Digital Converter (ADC) Peripheral Driver.

An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a discrete digital number.

The ADC always operates by successive approximation with 10-bit/12-bit resolution and has several input channels, plus an internal temperature 

sensor.

The ADC moudule always works as an programmable sequencer allowing the sampling of multiple analog input sources without controller 

intervention. The sequencer provides flexible programming with fully configurable input source, trigger events, interrupt generation.

A digital comparator function is included which allows the conversion value to be diverted to a digital comparator module. Each digital 

comparator evaluates the ADC conversion value against its user-defined values to determine the operational range of the signal.

The analog to digital converter (ADC) API provides a set of functions for dealing with the ADC.

Functions are provided to configure the sample sequencers and digital comparators, read the captured data, and handle the interrupt.


Contents

1. ADC Physical Block

2. ADC Functional Description

2.1 ADC Peripheral Pin Description

2.2 What is an ADC Sample Sequencer?

2.3 ADC Input Source

2.4 ADC Digital Comparator Unit

2.5 ADC Interrupt and Event


Detailed Description


*** CoX ADC Peripheral Interface. ***

http://www.coocox.org/cox/manual/interface/group__x_a_d_c.html#details

The xADC is the ADC Peripheral Interface of CoX. It defines some common macros and APIs.

Contents

1. How is the xADC Standard Defined?

2. API Groups

2.1 ADC Sequence APIs

2.2 ADC Processor Trigger APIs

2.3 ADC Digital Comparator APIs

2.4 ADC Interrupt APIs

3. Usage & Example

1. How is the xADC Standard Defined?

CoX ADC defines the APIs based on the following common functions:

Sequence Config:

Operation Mode:

single cycle

continuous

Trigger Source:

Processor(software)

External pin events:

Low Level.

High Level.

Falling edge.

Rising edge.

Sequence Step Config:

analog input source:

external input channel

internal temperature sensor

internal Vref

analog input type:

single-end

diffrence

Digital Comparator Unit

Interrupt Event

End convertion

Digital Comparator N match.

2. API Groups

The CoX ADC API is broken into four groups of functions:

those that deal with the ADC sample sequence,

those that deal with the processor trigger,

those that deal with configuring the digital comparator,

those that deal with interrupts.

2.1 ADC Sequence APIs

The sample sequences are configured with:

xADCConfigure()

xADCStepConfigure()

They are enabled and disabled with:

xADCEnable()

xADCDisable()

The captured data is obtained with:

xADCDataGet()

Sample sequence FIFO Overflow is managed with:

xADCOverflow()

xADCOverflowClear()

The DMA operation are enabled and disabled with:

xADCDMAEnable()

xADCDMADisable()

2.2 ADC Processor Trigger APIs

xADCProcessorTrigger() - generate the processor trigger

2.3 ADC Digital Comparator APIs

The digital comparators are configured with:

xADCCompConditionConfig()

xADCCompRegionSet()

They are enabled and disabled with:

xADCCompEnable()

xADCCompDisable()

2.4 ADC Interrupt APIs

Event callback function init with:

xADCIntCallbackInit()

Interrupts are enabled and disabled with:

xADCIntEnable()

xADCIntDisable()

3. Usage & Example

The followings show how to use the ADC APIs to initialize the ADC sample sequence, and get the AD convertion data to the buffer.

xSysCtlPeripheralEnable() to enable to GPIO,ADC Peripheral clock.

xSPinTypeADC() to configure the ADC pin.

xADCConfigure() to configure the operation mode and tigger source.

xADCStepConfigure() to configure the detail step AD convertion.

xADCIntEnable(), xIntEnable() to enable the interrupt.

xADCEnable() to enable the ADC.

xADCDataGet() get data in the interrupt callback function.



// *** adc.h ***

#ifndef __NXP_ADC_H
#define __NXP_ADC_H

#define  Vref   3280

extern void ADC_Init(void); // 初始化ADC口（AD7）
extern uint32 ADC_Read(void);   // 读取电压值（AD7）
extern uint32 ADC_To_Res(uint32 adc_value); // 把从AD7口读到的电压值转变为热敏电阻的电阻值
extern uint8 Res_To_Temp(uint32 res_value); // 把热敏电阻的电阻值转变为温度值
extern uint8 Fetch_sign(uint32 res_value);  // 检测温度是在零上还是零下

#endif


#include "nxplpc11xx.h"
#include "adc.h"

/*****************************************/
/* 函数名称：初始化ADC口（AD7）          */
/*****************************************/
void ADC_Init(void)
{
SYSCON->PDRUNCFG &= ~(0x1<<4);        // ADC模块上电
SYSCON->SYSAHBCLKCTRL |= (1<<13);     // 使能ADC时钟

SYSCON->SYSAHBCLKCTRL |= (1<<16);     // 使能IOCON时钟
IOCON->PIO1_11 &= ~0x9F;              // 把P1.11引脚选择模拟输入方式
  IOCON->PIO1_11 |= 0x01;               // 把P1.11引脚设置为AD7功能
SYSCON->SYSAHBCLKCTRL &= ~(1<<16);    // 关闭IOCON时钟
ADC->CR = (1<<7)|                     /* bit7:bit0   选择通道7作为ADC输入，即P1.11引脚 */
         (23<<8 )|                   /* bit15:bit8  把采样时钟频率设置为2MHz 48/(23+1)*/
         (1<<16 )|      /* bit16       硬件扫描模式  */
         (0<<17 )|        /* bit19:bit17 10位模式 */
 (0<<24 );           /* bit26:bit24 硬件扫描模式下这些位置0 */
}

/********************************************/
/* 函数功能：读取电压值（AD7）              */
/* 出口参数：adc_value, 读到的电压值        */
/********************************************/
uint32 ADC_Read(void)
{
uint32 adc_value=0;
uint8 i;

for(i=0;i<10;i++)  // 再连续读取10个电压值
{
delay_us(6);
adc_value += ((ADC->DR[7]>>6)&0x3FF);
}
adc_value = adc_value/10;  // 把读到的10个电压值取平均值
adc_value = (adc_value*Vref)/1024; // 转换为真正的电压值

return adc_value;  // 返回结果
}

/************************************************************/
/* 函数功能：把从AD7口读到的电压值转变为热敏电阻的电阻值    */
/* 入口参数：adc_value, 电阻值                              */
/* 出口参数：res_value, 电阻值                              */
/************************************************************/
uint32 ADC_To_Res(uint32 adc_value)
{
uint32 res_value;

res_value = (adc_value*10000)/(Vref-adc_value);

return res_value;
}

/************************************************************/
/* 函数功能：把热敏电阻的电阻值转变为温度值                 */
/* 入口参数：res_value, 电阻值                              */
/* 出口参数：temp, 温度值                                   */
/* 说    明：本函数根据MF58的数据手册编排，结果非常准确！   */
/************************************************************/
uint8 Res_To_Temp(uint32 res_value)
{
uint32 k;   // 斜率
int32 temp;  // 温度值

if( (res_value<29371)&&(res_value>18680) ) // 0~10摄氏度
{
k = 1069;
temp = ((29370-res_value)/k)+0;
}
else if( (res_value<18681)&&(res_value>12240) ) // 10~20摄氏度
{
  k = 644;
temp = ((18680-res_value)/k)+10;
}
else if( (res_value<12241)&&(res_value>8221) ) // 20~30摄氏度
{
  k = 402;
temp = ((12240-res_value)/k)+20;
}
else if( (res_value<8222)&&(res_value>5648) ) // 30~40摄氏度
{
  k = 257;
temp = ((8221-res_value)/k)+30;
}
else if( (res_value<5649)&&(res_value>3958) ) // 40~50摄氏度
{
  k = 169;
temp = ((5648-res_value)/k)+40;
}
else if( (res_value<47731)&&(res_value>29370) ) // -10~0摄氏度
{
  k = 1836;
temp = ((47730-res_value)/k)-10;
}
else if( (res_value<80361)&&(res_value>47730) ) // -20~-10摄氏度
{
  k = 3263;
temp = ((80360-res_value)/k)-20;
}
else if( (res_value<140001)&&(res_value>80360) ) // -30~-20摄氏度
{
  k = 5964;
temp = ((140000-res_value)/k)-30;
}
else if( (res_value<249600)&&(res_value>140000) ) // -40~-30摄氏度
{
  k = 10960;
temp = ((249600-res_value)/k)-40;
}

return((uint8)temp);   // 返回温度值
}

/*****************************************/
/* 函数功能：检测温度是在零上还是零下    */
/* 入口参数：热敏电阻的阻值              */
/* 出口参数：sign_sign, 1：零上          */
/*                      0：零下          */
/*****************************************/
uint8 Fetch_sign(uint32 res_value)
{
uint8 sign_sign;

if(res_value<29371)sign_sign = 1;
else sign_sign = 0;

return sign_sign;
}


//////////////////////////////////////////////////////////


*** UM10398 Chapter 25: LPC111x/LPC11Cxx ADC Rev. 12.1 — 7 August 2013 User manual ***

25.1 How to read this chapter

The ADC block is identical for all LPC111x, LPC11D14, and LPC11Cxx parts.
All HVQFN33 and LQFP48 packages support eight ADC channels. On the small
packages (TSSOP28/DIP28/TSSOP20/SO20), only five or six ADC channels are pinned
out (see Table 3).

25.2 Basic configuration

The ADC is configured using the following registers:

1. Pins: The ADC pin functions are configured in the IOCONFIG register block
(Section 7.4).

2. Power and peripheral clock: In the SYSAHBCLKCTRL register, set bit 13 (Table 21).

Power to the ADC at run-time is controlled through the PDRUNCFG register
(Table 44).

Remark: Basic clocking for the A/D converters is determined by the APB clock (PCLK). A
programmable divider is included in the A/D converter to scale this clock to the 4.5 MHz
(max) clock needed by the successive approximation process. An accurate conversion
requires 11 clock cycles.

25.3 Features

• 10-bit successive approximation Analog-to-Digital Converter (ADC).

• Input multiplexing among 8 pins.

• Power-down mode.

• Measurement range 0 to 3.6 V. Do not exceed the VDD voltage level.

• 10-bit conversion time 2.44 us.

• Burst conversion mode for single or multiple inputs.

• Optional conversion on transition on input pin or Timer Match signal.

• Individual result registers for each A/D channel to reduce interrupt overhead.

.END