A microcontroller, a digital device, can read, execute and transmit only digital signals. On the contrary, the outputs of the most of the transducers are analog in nature. Thus it is hard to interface these transducers directly with controllers. Analog-to-digital convertor (ADC) ICs are one way to make the analog input compatible with the microcontroller.
Using an external ADC adds complexity to the circuit. To avoid this complexity, PIC Microcontrollers have in-built ADC module which reduces the cost and connections of the circuit. This article explains the in-built ADC of PIC18F4550 controller.
As mentioned in the summary, a PIC microcontroller has inbuilt ADC for A/D conversion. The ADC module of PIC18F4550 controller has following specifications:
|
Bit 7 |
Bit 6 |
Bit 5 |
Bit 4 |
Bit 3 |
Bit 2 |
Bit 1 |
Bit 0 |
|
— |
— |
CHS3 |
CHS2 |
CHS1 |
CHS0 |
GO/DONE |
ADON |
|
CHS3:CHS0 |
Analog Channel |
Pin |
|
0000 |
Channel 0 |
RA0/AN0 |
|
0001 |
Channel 1 |
RA1/AN1 |
|
0010 |
Channel 2 |
RA2/AN2 |
|
0011 |
Channel 3 |
RA3/AN3 |
|
0100 |
Channel 4 |
RA5/AN4 |
|
0101 |
Channel 5 |
RE0/AN5 |
|
0110 |
Channel 6 |
RE1/AN6 |
|
0111 |
Channel 7 |
RE2/AN7 |
|
1000 |
Channel 8 |
RB2/AN8 |
|
1001 |
Channel 9 |
RB3/AN9 |
|
1010 |
Channel 10 |
RB1/AN10 |
|
1011 |
Channel 11 |
RB4/AN11 |
|
1100 |
Channel 12 |
RB0/AN12 |
|
Bit 7 |
Bit 6 |
Bit 5 |
Bit 4 |
Bit 3 |
Bit 2 |
Bit 1 |
Bit 0 |
|
— |
— |
VCFG1 |
VCFG0 |
PCFG3 |
PCFG2 |
PCFG1 |
PCFG0 |
