How to make a 8255 Based 8/16 Bit ADC

[cracksta]

Hi guys, i tried running a search for my project but found nothing

I know you guys can help with this as it should be simple for electronic minded pros.

My Task:

Interface an 8 or 16 bit ADC using digital I/O capabilities of the 8255 card. my main task is to drive the control lines of an analogue-to-digital convertor IC, so that it will convert a sample on demand and relay the resulting digital data through the 8255 I/O ports.

Now i know i need to create a C program on a PC, i should be able to do that on my own when i can get outputs from the 8255.

How do i start this as I dont have any of the equipment, i'll need a signal generator which a electronic store has a 'DIY' one.

i think i need: ADC (ADC 0804 or ADC 0808 with 8 ch MUX), latch (74ls378), buffer (74ls244) and S/H (LF398)

please help! I am not electronicly minded.

 

[cracksta]

Just found out the theory side is worth more, i.e 90% more!

if someone can write me a guide or something i may pay a little towards their efforts

 

[Papabravo]

A/D converters with direct digital outputs are getting pretty rare. So the 8255 may end up being pretty useless for your purposes. Most A/D converters have a bus interface. That said there are ISA prototype cards that let you create an I/O mapped peripheral device at one of several addresses. 0x300 to 0x31F is a typical range for such devices, but there are others. You probably need to be running something other than windoze.

 

[j.p.bill]

Since you are still n the planning phase, you need to decide on the precision of your conversion. 8 bits gets you one part on 256, 16 gives one in 65536. How finely you need to resolve your input is important.

You can get A to Ds with serial interfaces, which might make the input easier. Read up on things.

 

[cracksta]

thanks for the input,

it will be on a parallel connection, it has to be using an 8255 PPI (using it in the labs).

at the moment, all i want is to connect the ADC to the computer so that my C program can run, and all it does it take a analogue signal and convert to digital showing on the PC.

Actually making this can be done last, all i need now is to design how it all connects with diagrams and such, can some point me of the direction of data sheets and anything i need to read up regarding 8255 and ADC?

thank you!

 

[Analog]

Check out the ol' 7109 ADC. It has direct outputs that will couple to the 8255 nicely.

 

[ClydeCrashKop]

Search this forum for 8255 and LPT1. They have come up a few times.