ADS127* output Settling time
Part Number: ADS127L01
I'm trying to setup and use the ADS127L01 with Raspberry pi 3 model B, but it seems that I'm doing something wrong. I have two questions.
1. I have tied the CLK and SCLK and connected it to the SPI0_SCLK of RPi. Can this make any problem?
2. Previously when I use just simple 12-bit ADC, all that I did was lower CS, read the data, and raise CS. Here it seems that little more complicated. Is there any place that I can find some test source code for ADS127L01?
Alex SmithApplications Engineer | Precision Delta-Sigma Converters
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In reply to Alexander Smith:
Thank you for your advice! Following your suggestion, I have changed the configuration and checked the /DRDY, with CLK provided and START pulled high. I found that /DRDY pulses using an oscilloscope. It seems that the ADC is working (not damaged). However, I still get constant numbers from the ADC. I'm using SPI mode to communicate.
When I write (0,0,0,0), the return is (0,0,0,0)
When I write (18,0,0,0), the return is always (0,127,128,0), no matter which voltage is provided to the AINP of the ADC. (AINN is grounded).
(18 = 0001 0010, a command to read the most recent data.)
During the experiment START was pulled high, CS was pulled low, CLK = 10 MHz and SCLK = 100 kHz.
I will check if all the connections to the ADC are right. Anyway, thank you for your help.
In reply to Hongseok Oh:
Oh, the REFN was floating for some reason. Now I fixed it and it seems working better.
Depending on the voltage provided to AINP, I'm getting the MSB changed. However, only the first byte is changing, while the second and LSB keeps same (128 and 0). What should I do for this?
For example, during the 4-byte SPI communication:
Write buffer / Read buffer
(18,0,0,0) -> (N, 128, 0, 0) (N varies depending on the AINP value.)
Hello Hongseok, Additionally, can you provide some information on the input signals that you were applying from the previous post?
For the input signal, I hooked up a output of 10-bit DAC to the AINP of the ADC with a series resistor.
By the way, I have checked the register, tried some more measurement and got some progress.
1. I checked the register and found that all the values are set as default. This was done by write (0010 0000) , (0000 0111) (Read register 8 bytes) and subsequently reading 8 bytes. So at least the ADC is well reading and send back its register value without malfunctioning.
2. Then, I tried to read the different voltage (AINP) values. Strangely, sometimes it works fine but sometimes it doesn't. For example,
Output: 81, 126, 023, XXX(CRC) (The number changes little but does not change much, maybe due to fluctuation & noise of the input)
Output: 81, 255, 249, XXX(CRC) (2nd and 3rd bytes are always same over repeated reading)
Currently, I'm using the general purpose clock in the Raspberry Pi (GPIO #4). Can it make any problems?
Thank you for following up this problem!
Currently the clock is having 3.3 V magnitude, 4 Mhz frequency.
For the good and bad data, there is no difference in input signal. It is DC signal, and works fine at 1.0 V but bad at 1.1 V, and good again at 2.0 V. So I can't figure out what's wrong with it...
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