Circuit to convert TTL from BS1 to LV TTL

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I have a BS1 that I have to interface with a circuit that uses LV TTL.

The connection is as follows:
BS1 OutputPin --> TTL to LV TTL converter -->> LVTTLDevice input pin

It has to have 1200 baud speed. It needs ony one direction, from BS1 to LVTTL device

Anyone know how to do this?

Chris Savage

You could use a transistor pulled-up on the LVTTL side. The output would be inverted, but you could adjust for that in your serial parameters on the BS1. Take care.

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Chris Savage
Parallax Tech Support

Phil Pilgrim (PhiPi)

Looking at the 74LVT00 datasheet, as an example, it appears that the inputs are 5V-tolerant. Based on that, I don't really think you need to do anything special: just connect the pins. But to be sure, which LVTTL device will you be driving?

-Phil

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Thanks for you replies!

The chip I am going to interface is this one:
http://www.quasaruk.co.uk/acatalog/FM_Transmitter_Module.html

I am going to use SEROUT to drive the DataIn pin on that chip.

Phil Pilgrim (PhiPi)

The datasheet is pretty sketchy, isn't it? It claims an "LVTTL Operating Voltage" but doesn't actually say that the module is LVTTL-compliant. And there's no spec for the input voltage range, either. Given that, it's better to be safe than sorry. Chris's idea would work, as would any 74LVC gate, powered from the lower Vdd.

-Phil

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Thanks again. I will try the pullup thing. Yes, the datasheet is sketchy indeed. The module was only $5 though.