using a voltage divider to protect non-5V tolerant wireless module on SPI

The Arduino's output pins are at 5V. Some wireless modules are not 5V tolerant. So, to protect them, you can use a voltage divider to drop the 5V to ~3.3V. These wireless modules use SPI, so there are these pins involved:

MOSI MISO Clock Cable Select Interrupt

Is the voltage divider only needed on the MOSI, Clock, and Cable Select? The interrupt and the MISO are outputs from the module to the Arduino. As long as I don't accidentally make these pins outputs on the sketch, I should be OK?



I use 1k/2.2k dividers as these can go reasonably fast. A 1k in line with MISO and interrupt can be added to be paranoid should the pins get set wrongly as Arduino outputs.

What SPI speed? If using 4 MHZ, 8 MHZ clock speeds, you will have better signals with an active driver, such as 74HC4050 (powered from 3.3V) for signals to the device, "They have a modified input protection structure that enables these parts to be used as logic level translators which convert high-level logic to a low level logic while operating off the low-level logic supply." and 74HC125 (or one the single buffer SMD packages) for output enabled buffer on MISO coming from the device.