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Low Voltage on I/O Pins
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Please be positive and constructive with your questions and comments.

Low Voltage on I/O Pins

by Wingsparr on Thu Aug 06, 2020 6:56 pm

Hey,
I recently purchased a circuit playground express.
My I/O pins are not putting out voltage greater than 2.8v , when switched to high, or up, under a no load condition.
How can I increase the output voltage to at least 3v?
Or should you send me a replacement circuit playground express?
Other than the low voltage, the board seems to be operating correctly.
Thanks for any help you can provide!

Wingsparr
 
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Re: Low Voltage on I/O Pins

by dastels on Thu Aug 06, 2020 7:27 pm

How are you powering the board when you see the 2.8v on the output pins?

That's within spec for a logic High output from the SAMD21 powered at 3.3v Anything above 2.64v is to spec.

Is it not doing something you need it to do (i.e. are you interfacing with something that needs a higher HIGH level?

Dave

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Re: Low Voltage on I/O Pins

by Wingsparr on Thu Aug 06, 2020 7:56 pm

Hey, I powered the board with a 5v power supply, through a crickit board and a USB power supply directly connected to the board, and the crickit board removed. I need the board to activate some relays, that have a 3v-5v triggering voltage. The relays only require 2ma of current. The output voltage on the board at Vout was 5v and the 3.3v outputs are supplying 3.3v.
So when the board couldn’t trigger those relays, I disconnected them and measured the I/O outputs with no load attached.

Wingsparr
 
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Re: Low Voltage on I/O Pins

by dastels on Thu Aug 06, 2020 8:10 pm

Are you using this with the Crickit board? What relays are you using?

Dave

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Re: Low Voltage on I/O Pins

by Wingsparr on Thu Aug 06, 2020 9:08 pm

I had planned on using the crickit board for the connections, but it’s not required. I’ve attached a picture of the relay board. I did misquote the required current, it’s actually 3-5ma to trigger the relays.

DZS Elec 5V 4 Channel Relay Optocoupler Isolation Module Red Board 3-5V High and 0-1.5V Low Level Triggered Load AC 0-250V / DC 0-30V 10A SCM IO Control

So where on the Adafruit website does it show the specific output voltage variations on each pin? All I could find is the Pin description page, showing an output of 3.3v on the I/O pins.
Attachments
5064C88F-6383-47B9-B745-94DED53B4550.jpeg
5064C88F-6383-47B9-B745-94DED53B4550.jpeg (87.61 KiB) Viewed 38 times

Wingsparr
 
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Re: Low Voltage on I/O Pins

by dastels on Thu Aug 06, 2020 9:28 pm

Everything is in the SAMD21 datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/SAM_D21_DA1_Family_DataSheet_DS40001882F.pdf

You may need to boost the signal using a level shifter. You could shift them to 5v signals and power the relays with 5v. E.g. https://www.adafruit.com/product/1875

Dave

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Re: Low Voltage on I/O Pins

by petespaco on Sun Aug 09, 2020 2:36 pm

Have you actually measured the voltage coming on to the CPX board?
Is it possible the your "5 volt power supply USB" device isn't putting out what you think it is?

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Re: Low Voltage on I/O Pins

by Wingsparr on Sun Aug 09, 2020 6:01 pm

Yep, measured the supply and actually have normal voltage everywhere except on the I/O pins.
Very disappointed in it. I did buy what Dave recommended to up the voltage. Hope that works.

Wingsparr
 
Posts: 4
Joined: Thu Aug 06, 2020 6:47 pm

Please be positive and constructive with your questions and comments.