Texas Instruments TMS320F2837 D Series - Signed Input Voltages

Analog-to-Digital Converter (ADC)
TMS320F2837xD Microcontroller Workshop - Analog Subsystem 6 - 19
ADC Conversion Result Registers
16-Bit Mode
 Differential – two input pins (ADCINxP & ADCINxN)

Input voltage is the difference between the two pins
 External reference (VREFHI and VREFLO)
LSBMSB
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
AdcnResultRegs.ADCRESULTx n = a - d x = 0 - 15
ADCIN
x
P
Voltage
ADCINxN
Voltage
Digital
Results
AdcnResultRegs.
ADCRESULTx
3.0V 0V FFFFh 1111|1111|1111|1111
1.5V 1.5V 7FFFh 0111|1111|1111|1111
45µV
3.0V
-
45µV
1h
0000|0000|0000|0001
0V 3.0V 0h
0000|0000|0000|0000
Signed Input Voltages
How Can We Handle Signed Input Voltages?
Example: -1.5 V ≤ V
in
≤ +1.5 V
1) Add 1.5 volts to the
analog input
V
in
1.5V
ADCIN0
GND
VREFLO
-
+
R
R
R
-
+
R
R
ADCA
#include “F2837xD_Device.h”
#define offset 0x07FF
void main(void)
{
int16 value; // signed
value = AdcaResultRegs.ADCRESULT0 – offset;
}
2) Subtract “1. 5” from the digital result