1. 先看下ADS1120的结构图，ADS1120是个比较奇葩的ADC模数转换器，因为比较适用于热电阻之类的温度采集器。看下图，有个MUX多路复用器，应该是选择两个差分信号去测试，通过输入多路复用器 (MUX) 实现的两个差分输入或四个单端输入，一个低噪声可编程增益放大器 (PGA)，PGA，内部 PGA 提供高达128V/V 的增益。此 PGA 使得 ADS1120 非常适用于小型传感器信号测量 应用 ，例如电阻式温度检测器(RTD)、热电偶、热敏电阻和桥式传感器。
2. 看下寄存器，4个寄存器
3. 命令
4. 参考例程
VOID main(VOID)
{
signed long tData;
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
Init_StartUp(); // Initialize device
ADS1220Init(); // Initializes the SPI port pins as well as control
ADS1220Config(); // Set base configuration for ADS1x20 device
while()
{
/* Add specifc command for reading and writing ADS1220 here */
/* dFlag is set in the interrupt service routine when DRDY triggers end
of conversion */
if (dflag) /* check if new data is available */
{
tData = ADS1220ReadData(); /* get the data from the ADS1220 */
dFlag=;
}
/* other routines could be added here, such as change the mux setting */
} /* end of while(1) */
} /* end of main() */
其中配置函数比较重要，如下是1增益，也是就不变，然后ADS1220_MUX_0_G=0x80
void ADS1220Config(void)
{
unsigned Temp;
ADS1220ReadRegister(ADS1220_0_REGISTER, 0x01, &Temp);
/* clear prev value; */
Temp &= 0x0f;
Temp |= ADS1220_MUX_0_G;
/* write the register value containing the new value back to the ADS */
ADS1220WriteRegister(ADS1220_0_REGISTER, 0x01, &Temp);
ADS1220ReadRegister(ADS1220_1_REGISTER, 0x01, &Temp);
/* clear prev DataRate code; */
Temp &= 0x1f;
Temp |= (ADS1220_DR_600 + ADS1220_CC); /* Set default start mode to 600sps and continuous conversions */
/* write the register value containing the new value back to the ADS */
ADS1220WriteRegister(ADS1220_1_REGISTER, 0x01, &Temp);
}
ADS1220_MUX_0_G=0x80，那么看下寄存器，什么意思呢？就是测量AIN0引脚的电平，得出一个结论，如果要想测量4个通道，那么需要依次次修改MUX[3:0]，一个测量完再测试另外一个
读数据，这个例程比较简单，只测量了AIN0的电压，我们的应用是需要做2线PT100铂电阻温度测量，所以需要继续
long ADS1220ReadData(void)
{
long Data;
/* assert CS to start transfer */
ADS1220AssertCS();
/* send the command byte */
ADS1220SendByte(ADS1220_CMD_RDATA);
/* get the conversion result */ Data = ADS1220ReceiveByte();
Data = (Data << ) | ADS1220ReceiveByte();
/* sign extend data */
if (Data & 0x8000)
Data |= 0xffff0000; /* de-assert CS */
ADS1220AssertCS();
return Data;
}