Delta-Sigma-ADC in Assembler embedded in PBP, increasing resolution

[Ingvar]

The code checks if bit 2 of the high byte of the wordsized variable "counter" is set. If it is, the program has looped around 1024 times, if not it keeps looping.

There is really no math involved, 1024dec = 0400hex = 0000010000000000bin.

You don't want to check for anything more complicated than if a single bit is being set or cleared. That would slow the ADconversion down, not something you want to do. I'm not saying it can't be done, just that it wouldn't be very easy. Especially if you don't know assembler and i get the impression that you don't.

My advice is that you stick with 10 bits(1024) and when the conversion is complete you scale the result to your desired value. That can be done in various ways. Here's a few..... all will scale to 752.

Dummy = ADresult * 752
ScaledResult DIV32 1024

ScaledResult = ADresult */ 188 '752/1024*256=188

ScaledResult = ADresult ** 48128 '752/1024*65536=48128

/Ingvar

[selbstdual]

What about using

andlw 0x2F0 ; Are we done? (We're done when bit2 of
btfsc STATUS,Z ; the high order byte overflows to 1).

[Ingvar]

No, you can only check one byte(8bits) in one go. You're also trying to check several bits at the same time, only one is "allowed". If you really MUST check for something more complicated you'll need to rewrite the code yourself. Certanly possible but nothing i will help you with.

Good luck.
/Ingvar

PS. Is there a perticular reason why you can't use 10 bits and scale the result as i showed you in my last post? DS.

[selbstdual]

Where is the result stored - in result_l or result_h or are they the same ?

At U = Umax there should be a value of 1024.

[Ingvar]

Result_h is the high byte(8bits) of the wordsized(16bits) result. Result_l holds the lower 8 bits.

[selbstdual]

I don't understand this. How do you combine these two to get a Dez-number between 0 and 1023 ?

[Ingvar]

Ok, time for somebody else to step in. I don't have the patience, time and/or languageskills to explain how hex, binary and decimal correlates. I recommend that you buy a book that expalins the basics of "microcontrolling". Can't give you any advice on good books since i haven't needed one for 20 years.

Good luck
/Ingvar