Filip

Papilio Duo and Bidirectional Logic Level Converters

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Hello,

 

from the http://www.papilio.cc/uploads/Papilio/Papilio_DUO.pdf?raw=true' class="bbc_url">Papilio_Duo_schematic I assume that the not 5V tolerant pins are 3.3V ?  So if I would use Logic Level Converters I could make them 5V tolerant right ?

 

From the LTC3419EMS  comes out also 1.2V which confuses me even more (it is written:
 "delays 1V2 start" so probably it has noting to do with the CPIO pin Voltage)

 

Thanks

 

Filip.

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Hello Filip,

 

Please refer to the Papilio DUO hardware guide for more info about the 5V tolerance.

 

 

 

Please note that 5V tolerance means that you can connect 5V logic to these pins but the pins are not driven at 5V. The pins provide 3.3V which is high enough to trigger a "High" state for 5V logic levels. A few boards, such as RAMPS, need a full 5 Volts to work correctly. Unfortunately 5V tolerance will not work with these rare cases.

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The LTC3419EMS  Voltage Regulator chip provides 1.2V and 3.3V. 1.2V is for the core power reqiurements of the Spartan 6 FPGA. All user I/O is at 3.3V and the first 16 pins of the Papilio DUO have series current limiting resistors which makes them able to handle 5V parts connected to them without being damaged. They are 5V tolerant meaning they can connect to and communicate with a 5V part but they do not actually provide 5V outputs. This is going to work just fine in 99% of the applications you run into and you will not need to do voltage translation.

 

Jack.

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this are posts from this topic Output voltage on pins                                          (here for reference)

 

Hello Cactus,

 

All I/O on the Papilio Pro is 3.3V. You can connect to any 3.3V component with no problem. To communicate with a 5V part you need to put a 390 ohm resistor in between the Papilio I/O pin and the pins on the component you are connecting to. This will protect the 3.3V pin on the Papilio from too much current.

 

Jack.

 

 

Hello Cactus,

 

It depends what you mean by output. If you are driving 5V TTL logic then the 3.3V that is output by the Papilio is high enough to be considered a High signal. Please take a look at this:

https://learn.sparkfun.com/tutorials/logic-levels/ttl-logic-levels

You can see that 2V is considered a High logic level, so the 3.3V output by the Papilio will drive a 5V device just fine. 

 

Usually you only need to provide 5V for power which you can draw from the 5V pin on the Wing header. I have yet to run into a 5V device that needed anything more then that. RAMPS is the only thing I've heard of that is the exception and I've never really looked to closely to understand why....

 

Jack.

 

 

Actually, the logic detection level will depend on a large number of factors. If you have a stable (i.e., resistive) design, 3.3V should work just fine. If you have high inductive/capacitive paths, then you may have a problem.

If you can test a direct drive, and if it works, excellent. Otherwise you can get some level shifters, but they can be expensive ($2 for a 8-line), and you will need to take care of bidirectionality yourself - the "automatic" ones seldom work.

 

Alvie

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