Hi everybody.
I'm trying to use the AD7705 module with the famous library of "Kerry D. Wong "
(in this page there is the example of the code and the library AD7705/AD7706 Library Revisited – Kerry D. Wong).
I connected the positive output of a resistive divider to AN1+ and GND to the AN1- input.
The value I read on the serial monitor is 2.5, i think 2.5 is the reference value.
80mV comes out of the resistive divider and enters AN1+
Is the 80mV value too low to be read by the AD7705 module?
How do i change the gain value of the AD7705 module?
While you are posting the schematic include links to "Technical Information" on the AD7705 part/module you are using. Links to Amazon and other market place sellers are normally useless as they do not have the needed engineering information just enough to sell them.
That's the drawback when buying at Ali: you don't get schematics of the board so you must guess and you don't know what chip you get. My supplier wants 10 times the price of the board for the chip alone if I get 1000 pieces. I agree that a Chinese clone chip may be a bit cheaper but if it gets to these extremes I assume a fake chip.
You get the 2.5 value (the refernce voltage) if the chip returns only 1s on the SPI bus. This means either a wrong wiring or a bad chip. Regarding the price you paid I assume the later one.
Remember though that your board doesn't implement the reference design of the library's author. He uses a 2 MHz crystal while your board seems to carry a 4.91 MHz crystal which is at the top of the specification but inside the range (at least of the original chip). I would try to use the clock divisor in the clock register to at least half the input clock.
Hi everybody.
I continued with my tests.
I confirm that the wiring diagram is correct.
The module works perfectly and also very accurate, referring to my multimeter I have a difference in the reading of about 0.5mv / 1mv.
Kerry D. Wong has released two libraries where in the latest revision on the serial monitor i can read directly the mv value.
I don't have to elaborate the output subtracting the volt reference 2.5.
Probably in my first test I used an incorrect library.
I have two questions:
using the Kerry D. Wong library
How do I change the module gain?
how do i use two SPI modules at the same time? using the Kerry D. Wong library how can I set the address of the two modules?