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DIGITAL INPUTS: Feather nrf52832 + Motorwing + QTR-8RC Line
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

DIGITAL INPUTS: Feather nrf52832 + Motorwing + QTR-8RC Line

by troglodisme on Sat Dec 07, 2019 6:54 pm

Hi there,

I have been trying to build a simple line following robot using a Feather nRF2832 with a Feather Motorwing and a Pololu QTR-8RC digital sensor array (that you can see here if you are not familiar with it https://www.pololu.com/product/961)

Everything works fine on an Arduino Uno, I can read values from the sensor as expected using the library examples. When moving across to the Feather, I can't seem to get very nice readings from the digital input pins. I can only get 3 values, it looks like it's dividing the voltage in 4 sections (something like 1000, 780, 390, 0), really odd. Is there any settings on the nRF52 that I can play around with? I have tried using digital pins (27, 30) and analog pins (a0, a1 or 2, 3) - same results.

(I thought it could be something with the motorwing but I tried without it and it's the same result... I have also tried 2 different nRF52 boards just to be sure).

(I had initially tried using a Feather Huzzah as well, but then realised (?) there are not 2 digital pins available that are not shared with the SPI lines..)

Any help would be greatly appreciated!

Thanks, G
troglodisme
 
Posts: 35
Joined: Fri Apr 02, 2010 12:01 pm

Re: DIGITAL INPUTS: Feather nrf52832 + Motorwing + QTR-8RC L

by adafruit_support_bill on Sat Dec 07, 2019 8:13 pm

I'm not familiar with that sensor. But one difference between the UNO and the Feather is that the UNO is a 5v processor and the Feather is 3.3v. The sensor appears to rely on voltage decay time, and the Feather is starting with a lower voltage. I'd check with Pololu support to see if they have any recommendations for using their sensor with a 3.3v processor.

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Re: DIGITAL INPUTS: Feather nrf52832 + Motorwing + QTR-8RC L

by troglodisme on Sat Dec 07, 2019 8:21 pm

Many thanks for your reply.

Could you please elaborate on this? The voltage states 3.3v operating voltage which is why I have selected it to use with the feather system.
When testing on the Arduino I have been using the 3.3v power line, not 5 - but did you mean the actual input pins?

I am not too keen on using that sensor to be honest, I just need to make a line following robot and I'd like to use a wireless Feather of some sorts. Do yo have any further suggestions in this direction?

Thanks
troglodisme
 
Posts: 35
Joined: Fri Apr 02, 2010 12:01 pm

Re: DIGITAL INPUTS: Feather nrf52832 + Motorwing + QTR-8RC L

by adafruit_support_bill on Sat Dec 07, 2019 8:50 pm

As I said, we are not familiar with this sensor or the library. Pololu is the manufacture of the sensor and the authors of the library. They should be able to assist you with it.

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Re: DIGITAL INPUTS: Feather nrf52832 + Motorwing + QTR-8RC L

by troglodisme on Mon Dec 09, 2019 6:53 pm

I did not ask whether you were familiar with it or not, but thanks for repeating yourself.

Here is the post on Pololu's forum https://forum.pololu.com/t/qtr-8rc-with ... 3-3v/18440
troglodisme
 
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Joined: Fri Apr 02, 2010 12:01 pm

Please be positive and constructive with your questions and comments.