On teensy 3.5 (5v tolerant) I'm using SPI devices on the spi bus that are 5V. Everything is working fine
The devices themself have their own pullup, especially the GPIO expanders, to ensure their state is always HIGH whenever the mcu is powered down or rebooted.
^---------- CS line
during SPI transactions, we write HIGH and LOW to the pin to assert/deassert the chips, however, wouldn't that make the 3.3V and 5V share the same power?
Not having any issues currently for several months but...
Which would be preferable?
switching during transactions by:
pinMode(CS, OUTPUT) and pinMode(CS, INPUT)
( asserting to LOW then deasserting to floating pin so the external pullup will take over? )
or
1K resistor in series?
I would gather the pinMode is not as fast as digitalWriteFast method, any pointers?
The devices themself have their own pullup, especially the GPIO expanders, to ensure their state is always HIGH whenever the mcu is powered down or rebooted.
^---------- CS line
during SPI transactions, we write HIGH and LOW to the pin to assert/deassert the chips, however, wouldn't that make the 3.3V and 5V share the same power?
Not having any issues currently for several months but...
Which would be preferable?
switching during transactions by:
pinMode(CS, OUTPUT) and pinMode(CS, INPUT)
( asserting to LOW then deasserting to floating pin so the external pullup will take over? )
or
1K resistor in series?
I would gather the pinMode is not as fast as digitalWriteFast method, any pointers?