Q
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.
A
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