Serial Port Voltage of Ag Devices
Posted 2/22/2021 18:59 (#8851655 - in reply to #8850875)
Subject: RE: Serial Port Voltage of Ag Devices

Glenwood, Mn
co2shaun - 2/21/2021 23:20

Specifically I am wondering if I can pull Serial data from a trimble 252 into an arduino without a logic level convertor.

The answer is a fast no. Arduinos use ttl logic. Rs232 swings past 0v to negative. Hook up a standard rs232 device to an arduino will be a fast test in magic smoke for the arduino.

Great news is if you go to any electronics store, including Amazon, you can find yourself an “Rs232 to TTL adapter” and find your physical interface to suit. They are cheap and reliable.

To answer your question. Logic low on ttl is 5 or 3.3 v and on serial can be between -5 through -25v. Most use a max 232 or max 3232 which includes a “voltage doubler. So a 3.3v system will produce 6.6v and a 5v will produce 10v which is within specs.

Anyways, you need a converter, without a doubt, from an rs232 based machine to arduino.

Edit to add: the other reason to you need an rs232 converter is that the logic is inverted. Logic high on ttl (5v) is negative voltage on rs232 and logic low on ttl is Positive voltage on rs232.

Edited by Joe@RFDG 2/22/2021 19:06
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