AD7730: Parallel port of the PC

Document created by analog-archivist Employee on Feb 23, 2016
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AD7730 is directly connected to LPT1 port of a PC.
Din -> LPT1 :B0
Clock -> LPT1 :B1
Dout -> LPT1 :SEL INPUT

All pins of AD7730 seem well connected.

Problem is :
1. We send 32 clocks with Din=1 to reset the part - Ok.
2. We send   8 clocks with Din 00010000 (To read Status register).
3. We send 8 clocks and we read Dout wich answers 10010111
4. Dout stay at level 1 forever, even if we restart step 2.

5. If we repeat this restarting at step 1, Dout answer once but after it stay 1
forever.
6. Dout goes High (1) very slowly (9uS) while giving the 3 LSB of status
register on step 3.

Clock on time = 3uS
Clock off time = 6 uS.
Delay between steps 1,2,3,4, is some seconds because started manually by
pressing key on keyboard.

 

The AD7730 should not be connected directly to the parallel port of the PC. The
digital signals from a parallel port are very noisy, prone to voltage spikes
and over-shoots. In addition, the edges are poorly defined and this can cause
problems interfacing to  AD7730 (or any mixed signal IC).

Good practice is to place a schmitt trigger buffer between the P Port and the
AD7730. Refer to our evaluation board for further details. Or better still,
save your self some valuable time and buy the eval board.
http://products.analog.com/products/info.asp?product=AD7730

you can order the eval board from any of our distributors. You can find you
nearest contact at the following webaddress:
http://www.analog.com/world/corp_fin/sales_directory/distrib.html

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