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Topic: Level Shifter - LSF0108 (Read 713 times) previous topic - next topic

JIK14

Dear Forum

I am planning to purchase the Genuino 101, the specs seem awesome... its about time that they installed a SMPS on the input :)

But the IO pins and level shifting is not clear to me.

As I understand it one must utilise 5V TTL on all the GPIOs as there is a permanent level shifter (5 to3,3V) connected in series. Am I correct to say that 3.3V will not work correctly i.e VIH VIL versus VOH and VOL ?

For example if I use a DAC (MCP4725) what voltage should be used on the SCL/SDA pins (5V or 3.3V or both will work).

Additionally I see that the SCL&SDA pins are in parallel to pins A4 and A5. Does this mean if the I2C is in use I loose the functionality of 2 x Analogue inputs ? must one activate/deactivate these in the code ?

Thanks in advance.

nathancamp

I have several Arduino 101s and I assume they are the same except the name.  I don't believe that there is a voltage level shifter on them.  The outputs are 3.5 V and the inputs are 5V tolerant.  They are designed for 3.5V but will take 5V without problem.

One thing to keep in mind is the processor is intel, not a AVR processor, so a lot of libraries will not work out of the box.

JIK14

Hello,

The schematic clearly indicates a level shifter being (schematic attached). Thus I'm thinking if you drive the GPIO's with 3.3 V it wont work ?

Taking 5 V without damaging is one thing but correctly reading the HIGH /LOW states is my actual question.
For example some TTL devices consider VIH = 0.8*VDD. So depending if you utilise 3.3 V or 5 V you will not be in a clear High or lLow state ......

Nevertheless I am glad you mentioned about the libraries. would you recommend rather staying with the arduino UNO. I am actually a Leonardo fan but seeing that it is discontinued I am looking for greener pastures! I typically use the wire, serial , eeprom, Adafruit_MCP4725.h, i2c libraries

advice would be great.

Thanks


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