Reading a 16 bit Register

Bladactania · 07-03-2009, 11:37 PM

Greetings all... (I'm using Borland Turbo C/C++ 3.0)

I am using an ADC board (See Getting Started Sheet) attached to an SBC running DOS 6.2. There is only a sparse and seemingly rough documentation for the ADC. The board has a FIFO for reading the 24 channels. When I read from address BASE+0x0A (ADCFIFO), and then the internal pointers should advance to the next channel from the FIFO (Each address is actually 16-bit. I'm using inport(ADC_FIFO_REG) to read the data from the ADC. However, for some reason, the FIFO pointer actually moves 2 channels instead of 1. If I use inportb(ADC_FIFO_REG) (and therefore only get the LSB) the internal pointer only moves one channel. So I tried reading each byte of the FIFO in turn (I tried in both possible orders) which, again, caused the FIFO to advance 2 channels.

Is there another function or method I could use to read these registers? I have a feeling that there is an issue with the board itself, but then it could just be that I feel that way because of the pretty crappy state of the "manual" that they have for this board.

Any suggestions are welcome. I will post the full code if necessary.

Thanks,
Lee

**Salem** · 07-04-2009, 03:49 AM

How about inportw() ?

Bladactania · 07-04-2009, 01:23 PM

I get an undefined error for inportw()

Bladactania · 07-04-2009, 01:36 PM

I tried using inp(), inpw(), inport(), and inportb().

**Salem** · 07-04-2009, 02:14 PM

Write your own.
Call it inportw()
Containing a few asm instructions to input a 16 bit value from a port.

Bladactania · 07-04-2009, 03:02 PM

asm?

matsp · 07-04-2009, 03:05 PM

Code:

short x = inport(0x123);

should work right.

You will need to include "dos.h" (it may well be that it's a macro rather than a function, perhaps).

If that doesn't work, then as Salem says, you may need to write your own inline-assembler function.

--
Mats

Bladactania · 07-04-2009, 03:15 PM

Yeah that's what I originally tried (inport). I've never written inline assembler functions before... always fun to learn something new

07-03-2009, 11:37 PM	#1
Bladactania Registered User Join Date: Feb 2009 Posts: 278	Reading a 16 bit Register Greetings all... (I'm using Borland Turbo C/C++ 3.0) I am using an ADC board (See Getting Started Sheet) attached to an SBC running DOS 6.2. There is only a sparse and seemingly rough documentation for the ADC. The board has a FIFO for reading the 24 channels. When I read from address BASE+0x0A (ADCFIFO), and then the internal pointers should advance to the next channel from the FIFO (Each address is actually 16-bit. I'm using inport(ADC_FIFO_REG) to read the data from the ADC. However, for some reason, the FIFO pointer actually moves 2 channels instead of 1. If I use inportb(ADC_FIFO_REG) (and therefore only get the LSB) the internal pointer only moves one channel. So I tried reading each byte of the FIFO in turn (I tried in both possible orders) which, again, caused the FIFO to advance 2 channels. Is there another function or method I could use to read these registers? I have a feeling that there is an issue with the board itself, but then it could just be that I feel that way because of the pretty crappy state of the "manual" that they have for this board. Any suggestions are welcome. I will post the full code if necessary. Thanks, Lee
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07-04-2009, 03:49 AM	#2
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	How about inportw() ? __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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07-04-2009, 01:23 PM	#3
Bladactania Registered User Join Date: Feb 2009 Posts: 278	I get an undefined error for inportw()
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07-04-2009, 01:36 PM	#4
Bladactania Registered User Join Date: Feb 2009 Posts: 278	I tried using inp(), inpw(), inport(), and inportb().
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07-04-2009, 02:14 PM	#5
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	Write your own. Call it inportw() Containing a few asm instructions to input a 16 bit value from a port. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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07-04-2009, 03:02 PM	#6
Bladactania Registered User Join Date: Feb 2009 Posts: 278	asm?
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07-04-2009, 03:05 PM	#7
matsp Kernel hacker Join Date: Jul 2007 Location: Farncombe, Surrey, England Posts: 15,686	Code: short x = inport(0x123); should work right. You will need to include "dos.h" (it may well be that it's a macro rather than a function, perhaps). If that doesn't work, then as Salem says, you may need to write your own inline-assembler function. -- Mats __________________ Compilers can produce warnings - make the compiler programmers happy: Use them! Please don't PM me for help - and no, I don't do help over instant messengers.
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07-04-2009, 03:15 PM	#8
Bladactania Registered User Join Date: Feb 2009 Posts: 278	Yeah that's what I originally tried (inport). I've never written inline assembler functions before... always fun to learn something new
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