Teensy 4.0 I2C Bus issue (solved)

[Luca]

Hi, i've connected a bounch of components to a teensy 4.0 according to this diagram (i know that on the sd card slot positive and ground are swapped, that was made according to the footprint of the breackout board i used):

When i try to use the mpu6050 or the bmp280 i can't get a connection over i2c.
The connection are made trought a custom pcb designed around this schematic and it doesn't seam to be a connection kind of issue because i checked with a multimeter the continuity between i2c pins a power pins.
Any help will be apreciated.

 

[BriComp]

No i2c pull up resistors.

 

[Luca]

Thank you for answering. I checked the datasheet of the breackout board i used for the mpu6050 and it sad that it has 4.7k resistors between both sda scl and vin. That's why i didn't addd them in the schematic.

 

[BriComp]

The run the I2C scanner, it can be found at this address on your pc:
C:\Program Files (x86)\Arduino\hardware\teensy\avr\libraries\i2c_t3\examples\advanced_scanner

 

[MarkT]

The pull up resistors need to be to 3.3V, since that's the T4's IO voltage. Vin on the MPU6050 might not be 3.3V from what I know, so check that. 5V direct will kill the T4 immediately, so care is always needed with such things, though 4k7 resistors will happen to protect in this instance as they limit the current to something the protection diodes can handle.

 

[Luca]

The run the I2C scanner, it can be found at this address on your pc:
C:\Program Files (x86)\Arduino\hardware\teensy\avr\libraries\i2c_t3\examples\advanced_scanner

I tryed to upload it to the board but it gives me an error saying that it can't be compiled for a teensy 4.

 

[Luca]

The pull up resistors need to be to 3.3V, since that's the T4's IO voltage. Vin on the MPU6050 might not be 3.3V from what I know, so check that. 5V direct will kill the T4 immediately, so care is always needed with such things, though 4k7 resistors will happen to protect in this instance as they limit the current to something the protection diodes can handle.

Thank you for answering. I will try adding resistence between i2c and the 3.3 of the teensy. However i don't think that 5V will kill the board because on the website under the power tab it says that the teensy has a regulator connected to the VIN pin that lowers the input current to 3V3, thats why i am using 5V to power the whole circuit (when i am not using usb i have a buck converter that lowers the voltage of a small 2s lipo to 5V).

 

[Luca]

BTW i think that i've found the problem. I've might connected the bmp280 with an inverted footprint from the breackout board. I will check and tell you.

 

[jmarsh]

Thank you for answering. I will try adding resistence between i2c and the 3.3 of the teensy. However i don't think that 5V will kill the board because on the website under the power tab it says that the teensy has a regulator connected to the VIN pin that lowers the input current to 3V3, thats why i am using 5V to power the whole circuit (when i am not using usb i have a buck converter that lowers the voltage of a small 2s lipo to 5V).

5V on the IO pins will definitely kill a Teensy.