MichaelMeissner
Senior Member+
I was moving my fancy camera shutter release from the breadboard to a protoboard when I noticed something.
Part of the device has a Pololu level shifter (https://www.pololu.com/product/2595) that I use to drive neopixel/ws2812b LEDs. The level shifter has a 10K pullup resistor for each low voltage pin before hooking it to the MOSFET to shift the voltage to the high voltage pin. I hook up A3 for the neopixel lights, and also hook up A4/A5 for the i2c devices that need 5v instead of 3.3v. I hadn't gotten around to adding the normal 2.2K or 4.7K pull-up resistors to A4/A5, but I noticed it worked fine when I connected i2c devices to either 3.3v (using the original A4/A5 and 3.3v power) or 5v (using the level shifted A4/A5 and VIN power).
At the moment, I only use the bog standard 100kHz i2c bus for devices, and I've only tried it with a single i2c device with fairly short wires. I assume in this setup, that I might not be able to go to 400kHz for i2c, and I probably am limited to the number of devices to put on the i2c bus. Is this correct? At the moment, I don't care about higher speeds, and I generally only have an occasional i2c device, but I always like to know what the limits are in wiring up a board.
Thanks in advance.
Part of the device has a Pololu level shifter (https://www.pololu.com/product/2595) that I use to drive neopixel/ws2812b LEDs. The level shifter has a 10K pullup resistor for each low voltage pin before hooking it to the MOSFET to shift the voltage to the high voltage pin. I hook up A3 for the neopixel lights, and also hook up A4/A5 for the i2c devices that need 5v instead of 3.3v. I hadn't gotten around to adding the normal 2.2K or 4.7K pull-up resistors to A4/A5, but I noticed it worked fine when I connected i2c devices to either 3.3v (using the original A4/A5 and 3.3v power) or 5v (using the level shifted A4/A5 and VIN power).
At the moment, I only use the bog standard 100kHz i2c bus for devices, and I've only tried it with a single i2c device with fairly short wires. I assume in this setup, that I might not be able to go to 400kHz for i2c, and I probably am limited to the number of devices to put on the i2c bus. Is this correct? At the moment, I don't care about higher speeds, and I generally only have an occasional i2c device, but I always like to know what the limits are in wiring up a board.
Thanks in advance.