[edited by: GenevaCooper at 2:01 PM (GMT -5) on 5 Jan 2023]
The AD7745/AD7746 are a high resolution, S-? capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device...
AD7746 on Analog.com
Hi lkxaaa ,
I will be moving this thread to the proper forum. I hope someone from the community can assist you.
The No-OS drivers are a set of functions, registers and parameters that we provide to facilitate the programming of the device (in your case the AD7746) for any microcontroller. The No-OS drivers…
When I don't put a capacitor between EXCA and CIN(+), I have more than 1pF of capacitance between the breadboard holes. Is this because of the stray capacitance between the breadboards, can I calibrate to get the results I want?
The top half is the result of adding a 1pF capacitor in the middle.
The lower half is where no capacitor is applied.
By the way, when I subtract 0x80000, my capacitance value becomes large.
The procedure for calibrating an offset is described on page 23 of the AD7746 datasheet, and it's noted that board level stray capacitances often dominate.
Not sure how to explain the subtraction error - although you're mentioning 0x80000, with four zeros, should it be 0x800000 (an 8 with five zeros)?
thanks for your help.
I read in the file.I should first do the calibration of on-chip CAPDACs. .Is this the value of setting DACA?
1 When I want to use a single-ended capacitor input, should I set the value of DACA to 4.096pf when the output range of the capacitor is 0-8.192pf. or Use the following formula to set the DACA value.This formula appears in the circuit description of the CN0552.
2.Are subtractions from the above questions necessary in all cases 0x800000.
It sounds like you're over most of your difficulty with the driver and reading /writing / interpreting data. Can you either move this thread to the Precision ADCs forum, or start a new question specific to your calibration question? There are several answered questions on related topics, for example:
Per Mark's comment I agree that this question has been fundamentally answered. And will be closed out. There are several threads that Mark linked you to talking about the calibration routine which you should read over as a starting point, but if that doesn't answer your question, please submit a new question in the Precision ADCs forum for a more accurate answer.