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mbakpaul
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Joined: 2018-05-22 09:44
ADC on the DA14583

Hallo Dialog Team,
i am trying to sample values from a temperature sensor connected on P0_0. Everything functions fine but the value of the ADC never stays constant and hops with between +/- 5% of the actual value of the sensor. This happens even when the sensor has become stable. I tried monitoring the voltage on the OUT pin of the sensor using a Multimeter and a high resolution oscilloscope. The output value of the sensor doesn't change that much, so I was wondering if I did something wrong. Reading the value on the ADC port is based on the Battery Example (with single mode conversion and GP_ADC_ATTN3X to reduce the accuracy) .

Moreover, I would like to know for documentation purposes, which clock the ADC uses. I couldn't find anything exact concerning this matter. In the datasheet it says GP_ADC_CLK_SEL = 0 means the Internal high-speed clock is used whereas GP_ADC_CLK_SEL = 1 the digital clock is used. What are the exact values of these clocks?

Thanks in advance

Device: 
PM_Dialog
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Joined: 2018-02-08 11:03
Hi mbakpaul,

Hi mbakpaul,

Could you please clarify if you are using a custom board with the DA14583 or you are using any of our development boards? Probably noise is added between the sensor and the DA14583. There is not any available documentation regarding the clock generation of the ADC. As you correctly mentioned the ADC uses an Internal high-speed at ~200MHz. Can you please provide information of the sensor that you are using? Is it a 16-bit output?

Thanks, PM_Dialog

mbakpaul
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Last seen: 7 months 6 days ago
Joined: 2018-05-22 09:44
Hello Dialog Team,

Hello Dialog Team,
thanks for the reply! I am using a custom board with the DA14583 but I've tried connecting the output of the sensor on the ADC0 of the pro board and i still got the same results. I am using the LMT84DCKT of TI to monitor temperature changes. Its output is analog and gives a voltage between 0 and 1.5V.
Regarding the clock generation of the ADC, is it really possible to achieve 200MHz with a 16MHz Quarz? I can't really get it. Is it possible to configure the clock the ADC uses to sample ?

Thanks and Regards
Paul Mbak

PM_Dialog
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Last seen: 8 hours 45 min ago
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Hi mbakpaul,

Hi mbakpaul,

Could you please share the code snippet and the configurations that you are reading the ADC values? As I mentioned in my previous post the ADC uses an Internal high-speed at ~200MHz, so this clock is internally generated and not from 16MHz clock. Please check Table 177 of the DA1450 datasheet. The one selection (GP_ADC_CLK_SEL=0) sets as clock the internal clock of the ADC and the other selection (GP_ADC_CLK_SEL=1) chooses as clock of the ADC the system clock. Go with the 0 option (internal high-speed adc clock) since that is recommended by Dialog, the internal ADC clock is approximately 200MHz.

Thanks, PM_Dialog