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I'm looking to connect an old GPSlim236 device to my Arduino via serial comms. I have seen references online on how to connect the device but in the data sheet it says TTL level between 3V - 5V. Does this mean that the GPS can automatically switch between logic level 5V -3V when needed?

Here is the link to data sheet for the GPS - http://www.holux.com/JCore/UploadFile/3205400.pdf

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The datasheet says:

Power Supply

External Voltage: 5VDC +/- 10%

So I take that to mean you supply 5V to it.


Later on it says:

Transmit Data. From organizer to peripheral. (Voltage Level is 3.3V ~ 5.0V)

I presume that means that it will supply (or accept) 3.3V to 5V as a high level, and less than 3.3V as a low level. This is perfectly normal for an Arduino.


Does this mean that the GPS can automatically switch between logic level 5v -3v when needed ?

No I would not read it like that. If you read the datasheet for the Arduino processor chips it states things like an output high is a range of voltages, similar to what this device is saying. A "high" is not necessarily 5V exactly, it might be 4.7V, for example. However the Arduino input pins are similarly designed to take a range of voltages.


My confusion here is that the datasheet says 3-5v but what if I connect the device to a raspberry pi which (I think) only accepts 3v, would it still work?

Well, the datasheet says 5V +/- 10% for charging the internal battery. I'm not sure what your situation is if you are trying to run it from a Pi.

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  • Hi Nick, thanks for the reply. So does that mean if the GPS was connecting to a device that only accepted 3v as a logic high that it would work ? My confusion here is that the datasheet says 3-5v but what if I connect the device to a raspberry pi which (I think) only accepts 3v, would it still work ? Feel free to point me to a good document or source of information that can help me understand the difference between the different logic level. – AlanR Sep 7 '15 at 23:47
  • See amended answer. If you want to connect it to a Pi, you may need level shifters, because the 5 V output would be too high for it. – Nick Gammon Sep 8 '15 at 4:06

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