5V TTL?

Discussion related to "under the hood" OpenMV topics.
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kwiley
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Joined: Fri Dec 21, 2018 5:22 pm

5V TTL?

Postby kwiley » Wed Mar 27, 2019 6:06 pm

I see that OpenMV is described as 5V tolerant but 3.3V nominal. Since TTL detects high voltage as anything above 2V, does this imply that OpenMV should communicate over serial just fine in both directions with a 5V device? Assuming the messages would actually get through in both directions (I'm mildly concerned that mere 3.3V signals from OpenMV would fail to trigger high bits in a 5V device, but I guess that would be the other device's fault if 2V is the standard threshold, and I have no reason to anticipate such failure), would it otherwise be recommended to step the incoming 5V signals down to 3.3V for the OpenMV anyway? I mean, even if OpenMV "tolerates" 5V, does high voltage steadily "wear out" the board or otherwise decrease its lifespan? Or is that not how these things work? :D
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iabdalkader
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Re: 5V TTL?

Postby iabdalkader » Wed Mar 27, 2019 8:41 pm

3.3v TLL and 5v TLL devices are compatible, to a 5V system the minimum input for a high is >= 2v. It will Not damage the device (if it's 5v tolerant it's 5v tolerant), however note that not all pins are 5v tolerant (see the pinout).
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kwiley
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Re: 5V TTL?

Postby kwiley » Wed Mar 27, 2019 8:47 pm

Yes, I noticed the comment about the ADC/DAC line, but serial comms would be over the UART lines. I take your point though. Thanks.

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