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Forum: µC & Digital Electronics AD7705/AD7606 DAQ Module


von Jordan M. (jmiller22)


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Hello everyone,

I'm currently testing a small data acquisition project with the 
AD7705/AD7606 Data Acquisition Module (this one: 
https://easyelecmodule.com/product/ad7705-and-ad7606-data-acquisition-module/). 
The goal is to capture precise voltages from sensors via SPI. 
Unfortunately, nothing's working so far, the module simply isn't 
responding.

What's happening so far:

I have a stable 3.3 V supply, all GND references are correctly 
connected, and the SPI lines are soldered. When I try to read the data, 
the BUSY pin remains permanently LOW, even though I trigger the 
conversion start (CNVST) via SPI.

With the AD7705, I wanted to read data, but the return value always 
remains 0x0000 , apparently, the reset/init signal isn't being 
recognized correctly.


My questions:

Does a reset or init command have to be activated via hardware (reset 
pin) before data can be read? (For some users, this was the solution.) 
Are there any basic timing rules for SPI that are easily overlooked and 
lead to busy pin problems?

How do you typically measure the busy pin? Do I need to reduce the load 
or add a buffer?

I would be very grateful if anyone could help me get started or give me 
some tried-and-tested tips.

Regards and thanks in advance,
Jordan

von John (johnwebbe)


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You usually need to issue a proper reset/init sequence before the AD7705 
will respond – either via the RESET pin or by sending the reset command 
over SPI (32 consecutive 1s). Also double-check that your SPI mode 
matches the datasheet (CPOL/CPHA), since a wrong mode can keep BUSY 
stuck low. If BUSY never toggles, it’s often a sign the chip hasn’t left 
reset

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