What size additional pullups would you recommend?Īs for the UART1 and I2C0 conflict - there should be no problem. So how to I enable them on the Arduino 101? I know how to disable them on the Mega and Uno.

I believe you are correct that the mega has the internal pull-ups enabled by default (as well as the Uno). I am attaching the schematics for your reference. On the 521 this is LDO to convert from 5v to 3.3v.

It looks like the board has 4.7k pullups on the board already (attached), same for the propshield which is 3.3v powered while the 521 is powered from the 5v line.

Hi To answer some of your questions I am measuring the signal at the board pins while the sensors while the program is running. Looks like you don’t have any pullup on the sensor board. Looking at your scope picture, I see the voltage reading is about 3.3v. Make sure you are not enabling or using UART 1 since they both use the same pins on Arduino 101. The I2C 0 and UART1 are sharing the pins on the connector. If you are using Grove kit plus, they have place to install these on their board. You need to enable the internal pullup for these pins since there are voltage translator used on Arduino 101 and add pullup on your sensor board for these pins. Also mega firmware may be enabling their internal pullup.Īrduino 101 board does not have any pullup for the I2C. Slower communication without error can result in faster communication since it does not have to timeout and wait to recover from errors. I think if you zoom in with scope and look at the clock frequency for the Atmel mega, you will find that it is running slower then 400khz and that may be the reason it is running faster. I will do that next week and let you know. I don’t have the sensor you are using but I can test this using I2C RGB display board from my Grove kit plus.

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