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ads1115 input have some problems~

Other Parts Discussed in Thread: ADS1115

hi,

   I recently have a problem about single-shot mode of ADS1115Q1 for ADC, when supply power +5V for ADS1115, and supply +5V level signal or OPA +5v level for ADC input, the Conversion Register data also have 0x0000,(Config Register:0xc1e0), but when  supply current 20ma for ADS1115 IN0 input and use 250 ohm between IN0 and GND(AINP = AIN0 and AINN = GND), we can read  out Conversion Register data,and the result data is +5v, So I wan to know why ADS1115 have these question about it?

  • User4439175,


    First, I'm still a bit unsure of what you are measuring. Can you please show a schematic of what it is that you are measuring?

    I'm not sure, but it sounds like you are making two measurements, first you measure the supply and getting 0V instead of 5V, but then measuring the a 20mA current through a 250 Ohm resistor to ground and correctly getting a 5V measurement. Is this correct?

    There are only a few things that I think could be happening.

    It could be that the first reading didn't have the conversion start initiated. When the part is first powered up, it is in power-down single-shot conversion mode as a default. This means that the device still needs to have bit 15 of the config register written to as a 1 to begin a single conversion mode.

    Another possibility is that the input mux is written to incorrectly and the data that you are getting out of it is the wrong inputs. Seeing the schematic might help to diagnose this problem.

    Lastly is that maybe the address is wrong or the I2C communications is incorrect. I want to see the digital communications on an oscilloscope to make sure everything is correct.

    I had also made other comments and questions on another post. If you can, respond to those questions there, if I haven't asked them here already.

    e2e.ti.com/.../1582844

    Since I'm having a bit of a hard time with figuring out your problem, Would it be easier for you to send the question in Chinese? If you want to do that, be very detailed in your description of what you are measuring and what the problem is.


    Joseph Wu