UART with level shifter

Hello,

I want to connect the TK1 via UART with my device.
A level shifter (3.3 V <-> 5 V) was used because TK1 works with logic level of 1.8V.
My device operates at 3.3V logic level, so for this scenario, it is 1.8 V <-> 3.3 V.
Before i test the connection, i would like to be sure that the connection is correct (see Image).
Could someone check my UART connection? Has anyone here such a level shifter used (3.3V <-> 5V)?

http://bildr.no/image/TmxNeVVN.jpeg

Thank you,

Oleg

Theoretically this can work, but not sure about your level shift type, can you post datasheet of this level shift?
Can’t see the detail connections on your level shift board, but it should be correct if connect TK1’s RXD to your TXD, TK1’s TXD to your RXD.

Thank you for quick response!

Yes, the connection is

RX (mydevice) <-> TX (TK1)
TX (mydevice) <-> RX (TK1)

See Image
http://bildr.no/image/NW5IMHEy.jpeg

Here is the documentation of level shifter design
http://www.nxp.com/documents/application_note/AN10441.pdf

Can this level shifter use for shifting between 1.8 V - 3.3 V ?
The relationship between the LV-Side and HV-Side (1.8V - 3.3V) is approximately similar, as in 3.3 V - 5 V szenario.

FYI, I don’t think it would hurt to try (this is unlikely to harm anything), but internal resistors and drain substrate diodes might or might not do as expected at lower voltages.

Lots of inexpensive level shifters are out there for specific voltages which you would know are designed for that conversion. It probably isn’t worth the effort to use a shifter designed for higher voltages (even if it mostly works, it may not always work).

“Supply voltages other than 3.3 V for VDD1 and 5 V for VDD2 can also be applied, e.g., 2 V
for VDD1 and 10 V for VDD2 is feasible. In normal operation VDD2 must be equal to or
higher than VDD1 (VDD2 is allowed to fall below VDD1 during switching power on/off)”, per these words it can work for 1.8V - 3.3V, but as linuxdev said, it’d be better to use dedicate level shift.

I have now tested the UART connection and it works! :)
Thanks for your help! :)

Hi @oblv,

for a stable and robust serial connection you can get this shield board that has level shifting capabilities:
https://devtalk.nvidia.com/default/topic/923483/jetson-tk1/easytk1_io-v2-a-brand-new-jetson-tk1-io-shield-/

Walter