Asked
— Edited
I seemed to be having issues with I2C BlinkM's I keep adding the control to the layout and connect the blink M to one of the i2C ports and it disconnects the EZB, every single time. To make sure I have connected the wires correctly could someone point me to a call out that has the break down of the I2C ports, i.e +,-,c,d
Thanks in advance.
Thanks Jeremie, I'll give it a try today!
@Jeremie,
I need your input:
Q1) I traced the EZB pcb and it seems EZB does not have pull-ups on SDA, SCL lines, neither a resistor in series, can you confirm this ?
Regarding the Pull-Up values, several times I've used 4.7K with STM32F103, STM32F205 and other 3.3v micro-controllers. When adding 2 devices with same values 4.7K brings down to 2.35K and still works, but if i bring down below <1.5K i had problems.
I know there are other factors:
Q2) EZB I2c BUS Speed ? *** EDIT: The default value is 100 kbit/s and can be configured in the ARC
Q3) I never heard before the recommendation for 330 to 1K, Isn't the value too low ?
Q4) Can you explain why the recommendation is different for EZB when compared to other/same 3.3 micro-controllers ? *** EDIT 2: STM32F205 (EZB microcontroller) https://www.mouser.com/ds/2/389/stm32f205rb-956262.pdf page 114 When you have long wires, the series resistors limit the slew rate, but i believe we don't need them.