ADC configuration code meaning

[pp99]

ADC configuration code meaning in 16F877A

May I know what's are the meaning for each row code as below:

adcon0=0x00;
adcon1=0x00;

set_bit(adcon0,0);
set_bit(adcon0,2);

if(!(adcon0&4))
{
portb=adresh;
set_bit(adcon0,2);
}

and why need to change LVP_OFF to LVP_ON?

Thanks.

 

[alexan_e]

adcon0 and adcon1 control the ADC , check page 127-128 of the datasheet https://ww1.microchip.com/downloads/en/devicedoc/39582b.pdf

set_bit(adcon0,0); this sets bit0, it powers up the ADC
set_bit(adcon0,2); this sets bit2, it starts the conversion
if(!(adcon0&4)) checks if bit2 has become 0 which means that the conversion has ended

Alex

 

[pp99]

Then how about the &4 meaning?

Do you know what is the LVP meaning?

Thanks.

 

[ZASto]

Read the datasheet for 16F877A microcontroller, some 218 pages :grin:

 

[alexan_e]

Then how about the &4 meaning?

Do you know what is the LVP meaning?

Thanks.

Sorry for the late reply, my internet service was down yesterday.
You can read about bitwise operations in this tutorial AVR Freaks :: View topic - [TUT] [C] Bit manipulation (AKA "Programming 101")

adcon0&4 is using masking, it is the same as (adcon0 & 0b00000100) so adcon is ANDed with 0b00000100 which means that every bit except from bit 2 will be forced to give a result of 0 so using that you can actually check if bit2 (only) is 0 or 1.
Any value ANDed with 0 will always give a result of 0, any value ANDed with 1 will keep the value it had so (adcon0 & 0b00000100) can give two results, 0b00000100 when bit2=1 and 0b00000000 when bit2=0.

I don't use PIC so I don't know about the LVP but the datasheet says that it is used for low-voltage ICSP programming, I don't see a relation with the ADC.

Alex

 

[pudge]

what does the portb = adresh means?

 

[alexan_e]

ADRESH is the A/D Result High Register
The ADRESH:ADRESL registers contain the 10-bit result of the A/D conversion. When the A/D conversion is complete, the result is loaded into this A/D Result register pair.

You can find it in the datasheet

Alex

 

[ZASto]

@pudge: RTF Datasheet for the meaning of registers.

 

[dayanpad]

Re: ADC configuration code meaning in 16F877A

Dear pp99

As per your all Questions, I feel that your knowledge about MUC is too low
but all are replied well for you
however I think you should start from ground level before start ADC
we can help you
why don't you start here Nigel's PIC Tutorial Page
Chapter 1: World of Microcontrollers - Book: PIC Microcontrollers - Programming in C
wish you all the best