I recently bought a logic level converter for interfacing Arduino Uno with ESP8266. I had decided to use SPI communications between the two but after making all connections correctly it failed. After checking the shifter with a multimeter I found out the pins were high even with no signal applied (only HV and LV voltages are applied). This is fine for I2C but not for SPI. Is it possible to perform SPI with this shifter? If yes, then how?

enter image description here

Product link: here.

  • \$\begingroup\$ I guess it would be easier to help you if you could give more information about the level-shifter you’re using. \$\endgroup\$ Apr 11 '17 at 13:34
  • \$\begingroup\$ No circuit shown, no part numbers given. You must expect us to have a crystal ball? \$\endgroup\$
    – Bort
    Apr 11 '17 at 13:49
  • \$\begingroup\$ i could not find the circuit but here is an image \$\endgroup\$ Apr 11 '17 at 14:00
  • \$\begingroup\$ [amazon.in/Bi-Directional-Logic-Level-Converter-HACKER/dp/… \$\endgroup\$ Apr 11 '17 at 14:02
  • \$\begingroup\$ Still not much more helpful. And what is your goal? It is not clearly explained in your question. \$\endgroup\$
    – 12Lappie
    Apr 11 '17 at 14:09

The level shifter in your picture is very likely based on this schematic:

level shifter

The pull-up resistors will keep the lines HIGH while there are at high impedance. That's what you're measuring.

However, as soon one of the ports is connected to a non-hiZ OUTPUT pin, that won't be case anymore. The OUTPUT pin will then be able to drive LOW the port it is connected to, and then the other port will go LOW as well.

Conclusion: it should be fine for SPI.


The Amazon product page you've linked has a picture that contains a big hint too:

back side

  • \$\begingroup\$ ok i'll try once again \$\endgroup\$ Apr 11 '17 at 14:47

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