nrf24l01+ RF module and ATtiny85
Ralph Doncaster writes,
Nrf24l01+ modules are a cheap and low-power option for MCU wireless communication. Libraries are available for Arduino, and for arduino compatible MCUs like the ATTiny85. Controlling the nrf modules usually requires power plus 5 pins – CE, CSN, SCK, MOSI, & MISO. With pin-limited MCUs like the ATtiny85, 5 pins is a lot to tie up. On something like the Digispark, with PB3 and PB4 hard-wired to USB+ and USB-, using the nrf24l01+ modules might seem impossible. Another issue is that although the nrf inputs are 5v tolerant, Vcc must be between 1.9 and 3.6V. I’ve designed a simple solution to provide 3V power as well as control the modules with just 3 of the pins on the ATtiny85.
Controlling Nrf24l01+ RF module with 3 I/O pins