Hi,
I intend to make a precision Analogue to digital converter using ADS1158 and PIC 24EP512GU810. As I am a novice in this area and have never used the these devices, I do have a few questions before I purchase them.
1. Does the ADS1158 require any sort of programming? Or would it involve in just sending a word to the ADS1158 and it would perform the conversion.
2. For measuring 16 channels, would it be possible to measure a 300hz input signal accurately (i.e. within +/- 0.00001 volts).
3 Can the PIC 24EP512GU810 be programmed using the PIC kit 3?
It would be great to know the above details, as I these doubts popped up after I read the data sheets.
Thank you
Hi Ronnie,
Welcome to our forum! Can you provide any additional detail here with respect to your ADS1158 hardware and your reference voltage? Are you using our evaluation module or your own PCB? We can better address your second question with this detail.
For your other questions, the ADS1158 does not require programming if your application is comfortable with the deault settings of the device. We do not have any direct experience with the PIC kit 3, but if you can control an SPI port from your processor, I don't see where there would be any issues.
Regards,
Tom
Hi, Tom,
Thank you so much for taking your time to answer my query. I would be using my own PCB, but wold that make the device any less accurate?
I am pretty much in a hurry to build the device, but have come to realise that the 48 pin IC base is not available in the local market. Are there any other ways by which I can mound the device on the PCB?
Ronnie
We're here to help! Using your own PCB won't impact the absolute accuracy of the ADS1158 itself, but the things you put around it (the reference, the grounding structure, how you have your inputs routed) can certainly have an impact on accuracy. Send us your schematic and we'll be happy to review it for you.
By 48 pin IC base, do you mean a socket or are you looking for a pre-fabricated board that you can mount the chip to? If it's the later, you can try searching Proto Advantage or Digikey.
Dear Tom,
Thank you very much for your reply.
I do have another question for you how do I check if the ADS 1158 is working, without connecting the analogue signal inputs and not SPI communications?
I have made the following connections to check it:
AVDD, VREFP, DVDD, PWDN (bar), RESET (bar) connected to 5v.
AVSS, VREFN, DGND, CLKSEL, AINCOM connected to Ground.
XTAL1 and XTAL2 connected to a crystal.
When I check the out waveform at pin CLKIO (pin 13) there no clock waveform present. What do you think is the possible problem? Was it the right approach to check the device?
p.s. I have also connected the required capacitors.
By your description above, I believe there should be a clock output from the ADS1158. What crystal are you using and what capacitor values do you have?
Apologies for for the late reply, its just that I get time only over the weekends to work on the ADS.
I do believe the problem with the ADS not having an output clock waveform was due to the fact that I had not enabled the CLKENB bit. So I had to interface it with a microcontroller before I got an output waveform.
But now I have another problem:
I have set the reference voltage as 5v and 0v and am using it in unipolar mode. I do believe that for a 5v input I should get a FFFF and 0 volt a 0000.
But the problem is that the voltage is being divided by 2. So, I am getting a 7FFF for a 5 volt input.
What do you think the problem could be?
The output code of the ADS1158 is in binary two's compliment format. Take a look at Table 7 on page 23 of the data sheet, your conversion result for 5V in is correct - it should be 0x7FFF.