Hi Folks,
I am new to this forum, new to arduino and new to nRF24L01. Ofcourse I am, otherwise I would not ask such dumb questions.
I try to set up an ATtiny84 with an nRF24L01+ module to send data (temperature and humidity, what else? ) to an raspberry pi with another nRF24L01+ module.
As the TMRh20-Lib offers examples for Arduino, ATtiny84/85 and RPI i choose this lib. First of all i tried to get a connection between two RPIs with nRF24L01+ modules. After wiring everything up the connection was stable and everything was running like expected.
Then i tried to set up a ATtiny84 with the nRF-Module. I wired it up like explained in the sketch rf24ping85.ino and configured CE_PIN and CSN_PIN and set the addresses like they are set in the RPI-Example "transfer.cpp"
  ATtiny24/44/84 Pin map with CE_PIN 8 and CSN_PIN 7
Schematic provided and successfully tested by Carmine Pastore (https://github.com/Carminepz)
                 +-\/-+
  nRF24L01 VCC, pin2 --- VCC 1|o |14 GND --- nRF24L01 GND, pin1
              PB0 2|  |13 AREF
              PB1 3|  |12 PA1
              PB3 4|  |11 PA2 --- nRF24L01 CE, pin3
              PB2 5|  |10 PA3 --- nRF24L01 CSN, pin4
              PA7 6|  |9 PA4 --- nRF24L01 SCK, pin5
  nRF24L01 MOSI, pin7 --- PA6 7|  |8 PA5 --- nRF24L01 MISO, pin6
                 +----+
*/
// CE and CSN are configurable, specified values for ATtiny85 as connected above
#define CE_PIN 11
#define CSN_PIN 12
//#define CSN_PIN 3 // uncomment for ATtiny85 3 pins solution
#include "RF24.h"
RF24 radio(CE_PIN, CSN_PIN);
const uint64_t addresses[2] = { 0xABCDABCD71LL, 0x544d52687CLL };
//byte addresses[][6] = {
//Â "1Node","2Node"};
The sketch compiled without any errors and is running on the ATtiny84 as i can see in a serial terminal with a little Serial.println("Ping....") after calling the radio.write(...) function.
On the RPI in the transfer-example I removed some init-functions to the the RF24-init equal on RPI and ATtiny84.
This is what it looks like on the RPI:
 printf("RF24/examples/Transfer/\n");
 radio.begin();             // Setup and configure rf radio
//Â radio.setChannel(1);
//Â radio.setPALevel(RF24_PA_MAX);
//Â radio.setDataRate(RF24_1MBPS);
 radio.setAutoAck(1);          // Ensure autoACK is enabled
 radio.setRetries(2,15);         // Optionally, increase the delay be$
//Â radio.setCRCLength(RF24_CRC_8);
 radio.printDetails();
These are all the changes I made in the examples. Up to now I was not able to receive anything from the ATtiny84 at the RPI. I ran out of known options to check for.
Maybe some of you can point me to possible solutions?
Thanking you in anticipation
Jan