Problem with Arduino Nano Serial via a logic converter.

Projects Networking, Protocols, and Devices
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Hi all, i'm using a logic converter (txs0108e from TI) to communicate Arduino (Nano) with a 1.8V TTL Linux computer (Odroid XU4) via Serial. After some work as outlined in Odroid XU4 Serial Can't send to Arduino - ODROID I narrowed the problem to the logic converter can't keep the RX line to Arduino LOW when given a LOW signal from my Odroid. I suspect the logic converter had trouble determining who's the input. Since Arduino Serial Rx line is on a pull-up, it takes this high signal as input and feeds that to my actual input device: the Tx line on my Odroid. (but that's just my guess)

I plan to try some different logic converters but would really like to know the root cause for this problem and whether there are ways to salvage it, like adding pull-up or pull down resistors. I think this should be a easy problem for people experienced in EE, sadly I'm not one of them. And I hope the nice and knowledgeable people here can give me a hand.....

Here is the datasheet for the logic converter I'm using.

Thanks folks!

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Make a simple pencil drawing showing exactly how you have everything connected and post a photo of the drawing. Please DO NOT use Fritzing.

...R

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1024×768 89.3 KB

Hey Robin
Thank you for your reply, here's my diagram.

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The datasheet shows OE connected to GND and to the the 1.8v device. You don't reference it in your diagram.

I'm not sure whether it needs to be controlled by the 1.8v device or whether it is sufficient to connect it to GND permanently.

I note that the datasheet refers to the connections as A1 and B1 etc. It would be better if you use the standard nomenclature.

...R

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Sorry about the confusion in the diagram. OE is HIGH enable, and it is connected to my 1.8v input, i.e Vcca. The reason OE has a pulldown resistor in the datasheet is to ensure the device is in high-Z (off) mode during power up. After that it's high all the way.

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I am confused! But not the first time. Your data sheet shows 8-bit parallel movement of data between the two ports on the chip, but your pencil diagram shows a serial data connection.. ...

Which is it?

Paul