Adafruit carries a number of Bluetooth LE 4.0 modules in their store, notably the SPI (https://www.adafruit.com/products/2633) and UART (https://www.adafruit.com/product/2479) version. I have used the NRF24L01 module with ATtiny85 via SPI to transmit data in the past, and this uses 3 pins. I used the following setup to do so: https://www.hackster.io/arjun/nrf24l01-with-attiny85-3-pins-74a1f2.
My previous system consisted of ATtiny85s communicating with a receiver (Bluefruit Feather) via NRF24L01 radios. As the receiver got data, it sent it to an iPhone app that I wrote. Now, I would like to cut out this receiver and BLE straight to the iPhone, which supports multiple peripheral connections.
However, unlike the RF24 library, the Adafruit BLE SPI library needs the actual SPI library to compile correctly, which for some reason the RF24 library (this version: http://tmrh20.github.io/RF24/) doesn't. I don't quite get how the RF24 library can compile fine without the SPI library when targeting the ATtiny85 - Is there some way to get this to work similar to the RF24 library?
Alternatively, I think there is a way to do software UART on ATtiny85, which I know nothing about, so if there truly is no way to do SPI is UART possible?
I realize that this is a question best asked to Adafruit, which I have done, but I thought I'd post it here and see if anyone can help.