Hello all,
I am using the Adafruit Motor Shield V2 to control 2 DC motors along with a Naked Mega 4 which is a minimized version of the Arduino Mega. A link to that board can be found here.. I am having trouble with the SDA and SCL lines. I orginally used an Arduino Pro Mini with the shield and connected to its I2C pins (A4 & A5). My code and the shield worked without issue. However, when I switched to the Mega, the SDA and SCL pins cause the code to stop running and the motors don't run. I have multiple of these boards and I have double checked the issue isn't faulty boards or faulty solder/bridged connections.
Any ideas on what the issue could be? I am thinking that I may need pull-up resistors to those pins but I am not sure.
Thank you!
Please post a link to that naked Mega V4?
According to e.g. ATmega2560-Arduino Pin Mapping, A4 and A5 on the Mega are not the I2C pins.
sterretje:
Please post a link to that naked Mega V4?
According to e.g. ATmega2560-Arduino Pin Mapping, A4 and A5 on the Mega are not the I2C pins.
Correct! My wording was a bit confusing, I meant on the Pro Mini, the I2C pins are A4 and A5. On the Naked Mega they are 20 and 21, labeled SDA and SCL. A link to the board is here and here. I think the issue lies with the missing 10k pull up resistors on the naked mega. I added pull up resistors on a breadboard but I'm still not getting the desired effect.
Sorry, I thought that the link in your opening post was for the Adafruit shield.
No idea why it does not work if you use the correct pins and added pull-ups.
sterretje:
Sorry, I thought that the link in your opening post was for the Adafruit shield.
No idea why it does not work if you use the correct pins and added pull-ups.
I am sure I am using the correct pins but it's possible I could have wired the pull-up resistors wrong. I prototyped it on a breadboard in the following configuration: Naked Mega 5V to 10k resistor to SDA and SCL respectively such that the SDA and SCL pins get 5V input. I think this is correct but I could be wrong. I tested they were getting 5V with a multimeter as well.