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Topic: Another question re Arduino Due and shields (Read 162 times) previous topic - next topic

boylesg

Given the the logic level on a Due is 3.3V, can you safely plug all the shields available on ebay into a Due?

Are there level shifters built into the Due board between the pin sockets and and actual pins on the atmel chip?

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

boylesg

No and No.
So how do folks generally use the plethora a 5V devices from ebay.

For example how would you use one of the following with a due:


Or do would they use these devices separately with voltage dividers?




boylesg

Just measured Vcc on my Due's SPI header and it is 4.8V.

Is this an exception to the 3.3V logic level rule on a Due?

boylesg

I just measured Vcc on one of my data logger shield and for the SD card it is 3.3V so that is OK.

It was 5V for the RTC but there is no direct data connection between the SDA and SCL on the RTC to the relevant Arduino pins. I had to solder some connections in - now I know why.

CrossRoads

#5
Dec 04, 2016, 05:16 pm Last Edit: Dec 04, 2016, 05:18 pm by CrossRoads
Pin 2 on ISCP header comes from a boost regulator that outputs 5V, the regulator is rated for 1A, I don't know how much the parts used with are actually set up to support.

Pins 1,3,4 are the SPI pins that go right to the chip and should be used at 3.3V levels, with an Absolute Max of 4V.
6 is Gnd.

5 is MASTER-RESET, which is pulled up to 3.3V

Any Due shield used should have 3.3V IO signals, taking 5V power from the ISCP header or 5V from the power header (same signal) to make its own 3.3V supply.
Or it can get 3.3V from the power header, from the 1A rated 3.3V regulator on the Due.
Theoretically, a shield should use the IOREF signal on the power header to determine what IO level to use.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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