What is the difference between pin A4 and A3 (A5 and A2)?

[lazybaby7]

Hi I noticed that Pin A5 and A4 on Teensy 3.x are labeled as solid SDA0 and SCL0 while A2 and A3 are labeled with faint SDA0 and SCL0. May I ask what is the difference between pinA4 and A3(or A5 and A2)?

 

[KurtE]

Other than the obvious, that they are different pins. So you can do anlogInput on A5 or A2...

The A4 and A5 pins are the default pins you use for I2C. However on the Teensy you can alternatively use the A2 and A3 pin as alternate pins, by doing something like:
Wire.setSDA(A3) and likewise Wire.setSCL(A2)

 

[lazybaby7]

Thanks KurtE. Previously I do not use Wire.setSDA(A3) and Wire.setSCL(A2) so something that works on A4 and A5 does not works properly on A2 and A3.

Moreover, may I ask if A2,A3 can still be used as A4,A5 are being used ?

 

[PaulStoffregen]

If you want help with a problem, or if it might be a problem within the Teensyduino code that I should investigate, you MUST post complete code to reproduce the problem (aka, the "Forum Rule"...) A photo of how you actually connected things is probably also needed in a case like this.

 

[lazybaby7]

Hi Paul thanks for the comment. The problem has been solved. Previously I do not use Wire.setSDA(A3) and Wire.setSCL(A2). Now I am just wondering if A2,A3 can still be used as A4,A5 are being used.

 

[KurtE]

Unless you use I2C (Wire), all of these pins can do different things. Typically only one SDA and one SCL pin will be configured for I2C. So if for example you have A4 and A5 being used for I2C, then pins A2 and A3 are free to be used for other things like Analog input, digital input and output, Maybe PWM, maybe Touch...