ADC Library

ADC (Analog to Digital Converter) module is available with a number of PIC32 MCU modules. ADC is an electronic circuit that converts continuous signals to discrete digital numbers. ADC Library provides you a comfortable work with the module.

Library Routines

ADC1_Init
ADC1_Init_Advanced
ADC1_Get_Sample
ADC1_Read

ADC1_Init

Prototype	sub procedure ADC1_Init()
Description	This routines configures ADC module to work with default settings. The internal ADC module is set to: single channel conversion 10-bit conversion resolution unsigned integer data format auto-convert VRef+ : AVdd, VRef- : AVss instruction cycle clock conversion clock : 32*Tcy auto-sample time : 31TAD
Parameters	None.
Returns	Nothing.
Requires	MCU with built-in ADC module.
Example	ADC1_Init() ' Initialize ADC module with default settings
Notes	None.

ADC1_Init_Advanced

Prototype

sub procedure ADC1_Init_Advanced(dim Reference as word)

Description

This routine configures the internal ADC module to work with user defined settings.

Parameters

Reference: voltage reference used in ADC process.

Description	Predefined library const
Voltage reference:
`Internal voltage reference`	`_ADC_INTERNAL_REF`
`External voltage reference`	`_ADC_EXTERNAL_REF`

Returns

Nothing.

Requires

The MCU with built-in ADC module.

Example

ADC1_Init_Advanced(_ADC_INTERNAL_REF)  ' set internal reference used

Notes

Not all MCUs support advanced configuration. Please, read the appropriate datasheet before utilizing this library.

ADC1_Get_Sample

Prototype	sub function ADC1_Get_Sample(dim channel as word) as word
Description	The function enables ADC module and reads the specified analog channel input.
Parameters	`channel` represents the channel from which the analog value is to be acquired.
Returns	10-bit unsigned value from the specified `channel`.
Requires	The MCU with built-in ADC module. Prior to using this routine, ADC module needs to be initialized. See ADC1_Init and ADC1_Init_Advanced. Before using the function, be sure to configure the appropriate TRISx bits to designate pins as inputs.
Example	dim adc_value as word ... adc_value = ADC1_Get_Sample(10) ' read analog value from ADC module channel 10
Notes	The function sets the appropriate bit in the AD1PCFG registers to enable analog function of the chosen pin. Refer to the appropriate Datasheet for channel-to-pin mapping.

ADC1_Read

Prototype	sub function ADC1_Read(dim channel as word) as word
Description	The function initializes, enables ADC module and reads the specified analog channel input.
Parameters	`channel` represents the channel from which the analog value is to be acquired.
Returns	10-bit unsigned value from the specified `channel`.
Requires	The MCU with built-in ADC module. Before using the function, be sure to configure the appropriate TRISx bits to designate pins as inputs.
Example	dim adc_value as word ... adc_value = ADC1_Read(10) ' read analog value from ADCmodule channel 10
Notes	This is a standalone routine, so there is no need for a previous initialization of ADC module. The function sets the appropriate bit in the ADPCFG registers to enable analog function of the chosen pin. Refer to the appropriate Datasheet for channel-to-pin mapping.

Library Example

This code snippet reads analog value from the channel 1 and sends readings as a text over UART1.

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program Temperature_Sensor

' LCD module connections
dim LCD_RS as sbit  at LATB2_bit
dim LCD_EN as sbit  at LATB3_bit
dim LCD_D4 as sbit  at LATB4_bit
dim LCD_D5 as sbit  at LATB5_bit
dim LCD_D6 as sbit  at LATB6_bit
dim LCD_D7 as sbit  at LATB7_bit

dim LCD_RS_Direction as sbit at TRISB2_bit
dim LCD_EN_Direction as sbit at TRISB3_bit
dim LCD_D4_Direction as sbit at TRISB4_bit
dim LCD_D5_Direction as sbit at TRISB5_bit
dim LCD_D6_Direction as sbit at TRISB6_bit
dim LCD_D7_Direction as sbit at TRISB7_bit
' End LCD module connections

dim temp as float
    txt as char[16]

' Convert ADC value to Celsius degrees format
sub function ADC_to_degC() as float
  result = ADC1_Get_Sample(8)         ' Read ADC value from AN8 pin
  result = (((3.25/1024) * result - 0.5) * 100)
end sub

main:
  CHECON = 0x32
  AD1PCFG = 0xFFF7                      ' Configure AN8 pin as analog I/O
  ADC1_Init()                           ' Initialize ADC
  Delay_100ms()
  Lcd_Init()                            ' Initialize LCD
  Lcd_Cmd(_LCD_CLEAR)                   ' Clear LCD
  Lcd_Cmd(_LCD_CURSOR_OFF)              ' Turn cursor off
  Lcd_Out(1, 1, " Temperature:   ")

  while(TRUE)
    temp = ADC_to_degC()                ' Convert ADC value to Celsius degrees format
    FloatToStr(temp, txt)
    Lcd_Chr(2,13,223)                   ' Print degree character, 'C' for Centigrades
                                        ' Different LCD displays have different char code for degree
    Lcd_Chr(2,14,"C")                   ' If you see greek alpha letter try typing 178 instead of 223
    Lcd_Out(2, 5, txt)                  ' Display value on the LCD
    Delay_1sec()                        ' 1 second delay
  wend
end.

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