I've been having problems getting I2C to work on Due to an Adafruit Motor Shield V2.
The Motor Shield uses SCL1 & SDA1 (wire1, not wire in wire.h). Their other sensors may be similar
I've been looking over the schematic and I can find the 1K pull-ups for I2C0, but not for I2C1.
Is it then true that one must add pull-up resistors for SCL1 and SDA1 , but not for SCL0 and SDA0?
I also noticed that these route to SAM3X8 pins 70 & 9, but the variant.h file I have with the 1.5.6-r2 IDE says pins 70 & 71 ????
Is that correct?
Sorry, upon further searching I found this was answered here:
Just in case, here other info:
Regarding the I2C1 pins:
70 and 9 are the physical pin numbers for SCL1(PA18) and SDA1 (PA17).
71 and 70 are the digital pin numbers for SCL1(PA18) and SDA1 (PA17).
For a reference in the forum, look at Graynomad’s DUE pinout diagram:
For Atmel references:
See Table 4-3 (page 19) of Atmel doc11057
For Arduino reference:
See DUE schematic:
Regarding the pull-up resistors:
For I2C0 you don’t need pull-up resistors.
For I2C1 you need pull-up resistors. I have used 1K ohm without problems.