I recently realized that you can customize the clock speed for each SPI chip that you talk to, since only one is ever listening when you enable its chip select pin.
But I was wondering what you can get away with on I2C.
I currently have a PCF8523 RTC as the sole chip on my I2C bus running at 400kHz. I would love to add a MCP23008 8 bit I/O expander running at 1.7MHz, but the RTC tops out at 1MHz. Can i run the bus hot for the i/o expander at 1.7MHz, or am i running the risk that the RTC might respond in error to what it sees as a garbled, too fast message on the bus?
With I2C, is my fastest clock speed limited to the slowest component on the bus?
Are their any low-cost (compatible?) RTC’s that I could swap out that would run on a faster bus?