help on ADC0809

[[email protected]]

This one is a problem that I have encountered and I thought someone
might be able to help.

I interfaced a ADC0809 with the parallel port of the computer working
with operating system Win98. The start of conversion (SOC) pulse is
sent by the program which then waits for the End of conversion (EOC)
from the ADC. When the ADC responds with EOC, the 8 bit data is read.

So far so good. Now if the program is put into a loop a 50ms delay has
to be given before sending the second SOC. If less delay is given the
data given by the ADC is zero. If 50ms delay is given the card
captures
sine, trianglur and square waves very well of frequency 1-2Hz.

(50ms delay corresponds to 20Hz sampling and since I demanded 10 data
per cycle, I capture 2Hz waves)

Datasheet of ADC0809 says this delay is not required and the sampling
frequency is 100KHz. However, I dont get this. I wrote to National
semiconductors and they are of no help. After initial enquiries when
they realised trouble, they just stopped communicating.

I have looked up the net and dont see anyone else talking of this
problem.
So please help!!!!

Best if you mail it at [email protected] or/and [email protected]

bye for now
Arun

 

[[email protected]]

This one is a problem that I have encountered and I thought someone
might be able to help.

I interfaced a ADC0809 with the parallel port of the computer working
with operating system Win98. The start of conversion (SOC) pulse is
sent by the program which then waits for the End of conversion (EOC)
from the ADC. When the ADC responds with EOC, the 8 bit data is read.

So far so good. Now if the program is put into a loop a 50ms delay has
to be given before sending the second SOC. If less delay is given the
data given by the ADC is zero.

Please describe your conversion clock input to the chip.

 

[Rich Grise]

This one is a problem that I have encountered and I thought someone
might be able to help.

I interfaced a ADC0809 with the parallel port of the computer working
with operating system Win98. The start of conversion (SOC) pulse is
sent by the program which then waits for the End of conversion (EOC)
from the ADC. When the ADC responds with EOC, the 8 bit data is read.

So far so good. Now if the program is put into a loop a 50ms delay has
to be given before sending the second SOC. If less delay is given the
data given by the ADC is zero. If 50ms delay is given the card
captures
sine, trianglur and square waves very well of frequency 1-2Hz.

(50ms delay corresponds to 20Hz sampling and since I demanded 10 data
per cycle, I capture 2Hz waves)

Datasheet of ADC0809 says this delay is not required and the sampling
frequency is 100KHz. However, I dont get this. I wrote to National
semiconductors and they are of no help. After initial enquiries when
they realised trouble, they just stopped communicating.

I have looked up the net and dont see anyone else talking of this
problem.
So please help!!!!

Best if you mail it at [email protected] or/and [email protected]

We don't send answers by email. If you could bother to find the NG to post
the question, you can bother to find the NG again to look for answers.

Good Luck!
Rich

 

[Paul E. Schoen]

This one is a problem that I have encountered and I thought someone
might be able to help.

I interfaced a ADC0809 with the parallel port of the computer working
with operating system Win98. The start of conversion (SOC) pulse is
sent by the program which then waits for the End of conversion (EOC)
from the ADC. When the ADC responds with EOC, the 8 bit data is read.

So far so good. Now if the program is put into a loop a 50ms delay has
to be given before sending the second SOC. If less delay is given the
data given by the ADC is zero. If 50ms delay is given the card
captures
sine, trianglur and square waves very well of frequency 1-2Hz.

(50ms delay corresponds to 20Hz sampling and since I demanded 10 data
per cycle, I capture 2Hz waves)

Datasheet of ADC0809 says this delay is not required and the sampling
frequency is 100KHz. However, I dont get this. I wrote to National
semiconductors and they are of no help. After initial enquiries when
they realised trouble, they just stopped communicating.

I have looked up the net and dont see anyone else talking of this
problem.
So please help!!!!

Best if you mail it at [email protected] or/and [email protected]

bye for now
Arun

It may depend on how you are implementing the 50 mSec delay. The internal
timer of a PC is just about 50 mSec, so you may have granularity issues.
Please respond to the NG postings so all may learn.

Paul