Connecting incompatible Grove components (5V, AVR)

I seem to have ordered a set of incompatible items from the SODAQ shop (a warning would have been nice ;-)) and was wondering if there is a general and safe way to make them compatible.

This concerns voltage and drivers.

The Autonomo runs on 3.3V which means that (at least) the following Grove items will probably not work correctly:

  • RGB chainable LED (seems to work on 3.3V, albeit buggy)
  • 125 kHz RFID reader
  • IR reflective sensor
  • Bee socket

Supposing 5V is available (through USB or otherwise) what is the best way to go at this? I can feed 5V into the Grove element, but what needs to be done to the signals? Will feeding 5V signals to the Autonomo do damage? Will components reliably see 3.3V as high? What’s the best way to convert signals, if needed?

Regarding drivers/libraries I see that for instance the IR examples include avr/io.h which is apparently an API for AVR based Arduino’s, and as Autonomo is ARM based they are of no use. Is there a general way to adapt such code or are the architectural differences so big that re-writing the library is a more viable option?

There is a 5V pin on the Autonomo. You just cant use the easy grove connector.
The Bee socket and RGB led work perfectly on 3.3V.
I didnt try the other two.
For the bee socket it depends on your bee. All SODAQ Bees are 3.3V so 5V could damage them.

The input is 3.3V the maximum it can read.

AVR - ARM.
The Autonomo has the same chip as the Arduino m0 / Zero.
Maybe there is an example for that board.

If you cant find any then I can look into that for you.
Usually there is not much change needed.

If you are sending a signal to a 5V device, you might be able to get away with 3.3V levels.
It would depend on the receiving device and whether it is TTL or CMOS:
www.allaboutcircuits.com/textbook/digital/chpt-3/logic-signal-voltage-levels/

Receiving at 5V logic levels will certainly damage the Autonomo, if connected directly, as the absolute maximum should not exceed 3.6V [supply +0.3V]. [See the Samd21 datasheet p.925 table 36-1.]

One solution might be to use a level shifter such as:
https://www.coolcomponents.co.uk/logic-level-converter-bi-directional.html

However, there still remains the issue of the 5V pin only being available, as a power source, when the USB is connected.

If you fail to get it going, you can return it to us and we will fully refund it!