Implementation of LED connection monitoring function

RE: Implementation of LED connection monitoring function

haakonsh — Mon, 26 Jun 2023 11:36:47 GMT

Hey KemonCacke,

I've moved this ticket to the 'Private' realm so we can share confidential informaion.

I would like to review your schematics and layout files for any issues, and to understand your circuit better.

If the ADC output is not within +/-2lsb10 of zero when the input is at GND level, then you need to run offset calibration.

If the ADC output == DC power supply sweep, then there is no issue with the ADC itself.

If the ADC input is floating then it is likely to float close to VDD potential, but with a fair bit if noise. Often as much as +/- 40 12-bit lsb. If there's less than +/-5 12-bit lsb of noise then there might be a short between the GPIO and VDD.

BR,
Håkon Holdhus

RE: Implementation of LED connection monitoring function

LemonCake — Fri, 23 Jun 2023 05:43:52 GMT

Thank you for your assistance.
Thank you very much for answering my question.

When you say 'I cannot read the value', do you then mean that the value is as you have shown in the original ticket, or is it somehow failing?

With the LED attached to the board, the ADC value should be about 1800, but it outputs a value of about 2800, which is much larger than that, and when the LED is removed, it should output a value of about 1400 or less, but it outputs a value of about 2700, so I am wondering if there is some kind of We believe that an error has occurred.

Have you verified the voltage going into AIN5 by another device, such as a oscilloscope or multimeter?

I have increased the ADC value by 0.5[V] from 0~2.5[V] using a stabilized power supply and read the ADC value at each of them, and a realistic value is output. Therefore, there seems to be no problem with the output of ADC values.

By the way, the ADC value is output at about 2700 even though the LED is not installed, but it is calculated to be about 1.8[V]. This is the default value of the power supply voltage, so there is a possibility that this is related to the problem, but we do not know how to solve it specifically.
Thank you in advance for your help.

RE: Implementation of LED connection monitoring function

Karl Ylvisaker — Tue, 13 Jun 2023 14:53:01 GMT

Hello,

[quote user="Kosuke"]Thank you for your assistance.
Thank you very much for your reply.[/quote]

No problem at all, I am happy to help! :)

[quote user="Kosuke"]As for the details of what I am doing, I would like to read the voltage divided by a resistor at AIN5 when the 8.2V input is switched on and off, as shown in the figure below. However, when I input 1.2V to AIN5 when the supply voltage is 2.7V, I cannot read the value.[/quote]

Thank you for providing the diagram, this makes your setup much easier to understand.
When you say 'I cannot read the value', do you then mean that the value is as you have shown in the original ticket, or is it somehow failing?
Have you verified the voltage going into AIN5 by another device, such as a oscilloscope or multimeter?

With the configuration shown above your input range should be 0-VDD, so that should not be the problem here either.
Just out of curiosity from what you wrote in the original ticket, what is the result if you use the following config:
NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD)?
When you initially tried to measure GND, did you then short the AIN5 with GND directly, through an external jumper or similar?

Best regards,
Karl

RE: Implementation of LED connection monitoring function

LemonCake — Tue, 13 Jun 2023 08:59:20 GMT

Thank you for your assistance.
Thank you very much for your reply.
As for the details of what I am doing, I would like to read the voltage divided by a resistor at AIN5 when the 8.2V input is switched on and off, as shown in the figure below. However, when I input 1.2V to AIN5 when the supply voltage is 2.7V, I cannot read the value.
Please please help me.

RE: Implementation of LED connection monitoring function

Karl Ylvisaker — Mon, 12 Jun 2023 07:16:03 GMT

Hello,

Thank you for your extreme patience with this. I have been away from DevZone for some days at the end of last week, but now I am back.

[quote user=""]Specifically, I am setting the AIN value and outputting the ADC value of the input side and the GND side, i.e., the raw data at the time of AD conversion, but the value of the GND side does not become 0, and the value is as shown in the first image below.[/quote]

When you say this, do you mean that you keep the AIN5 configuration the same, and the externally connect the chosen AIN5 between the LED and the GND, to measure? Or do you mean that you reconfigure it in the code, and see no difference? In case of the latter, could you elaborate on exactly how you do this?

If you could also share a simple diagram of your setup, just so that I can make sure that I have understood your setup and intentions correctly.

Best regards,
Karl