Connection between ATTiny85 and RaspberryPi3 with nRF24L01+

Question

I'm hoping someone can help me since I've been struggling with this all weekend. I've got 2 nRF24L01+ breakout cards and I'm trying to send data from a ATTiny85 to a Raspberry Pi 3.

My setup is (the attiny85 breadboard has a 3.3V power supply):

ATTiny85

RaspberryPi3

And the code I'm testing is for the ATTiny85:

#define CE_PIN 3
#define CSN_PIN 4
#include "RF24.h"
RF24 radio(CE_PIN, CSN_PIN);
const byte addr[6] = "00001";
int count = 0;
void setup() {
 radio.begin();
 radio.openWritingPipe(addr);
 radio.setPALevel(RF24_PA_MIN);
 radio.stopListening();
}
void loop(void){
 radio.write( &count, sizeof(count) );
 count++;
 delay(1000);
}

And for the Raspberry Pi 3:

#include <cstdlib>
#include <iostream>
#include <sstream>
#include <string>
#include <unistd.h>
#include <RF24/RF24.h>
using namespace std;
// Setup for GPIO 22 CE and CE0 CSN with SPI Speed @ 8Mhz
RF24 radio(RPI_V2_GPIO_P1_22, RPI_V2_GPIO_P1_24, BCM2835_SPI_SPEED_8MHZ);
// Radio pipe addresses for the 2 nodes to communicate.
const uint8_t addr[6] = "00001";
int main(int argc, char** argv){
 radio.begin();
 radio.setPALevel(RF24_PA_MIN);
 radio.openReadingPipe(1, addr);
 radio.startListening();
 // Dump the configuration of the rf unit for debugging
 radio.printDetails();
 int count = 0;
 while (1)
 {
 while ( radio.available() )
 {
 radio.read( &count, sizeof(count) );
 printf("Count: %d\n", count);
 }
 sleep(1);
 }
 return 0;
}

• Mikael Patel: Double check MISO/MOSI on ATtiny. They are DO and DI not MISO and MOSI (which are used when programming).
• Jeff Williams: Double check what about them? As far as I understand, the RF24 library supports the attiny's USI for SPI
• Mikael Patel: You might have got the wiring wrong; NRF24/MISO => ATtiny85/DI (Pin 5), MOSI => DO (Pin 6).
• Jeff Williams: @MikaelPatel thanks! That looks like it could be the problem. I have been going off the chip pinout from the datasheet (MOSI pin 5, MISO to pin 6). However, I see now that tmrh20.github.io/RF24/ATTiny.html has them listed the other way around, like you say. I'll test when I get home tonight.
• Mikael Patel: Yes, USI uses DO(utput) and DI(nput). The MISO/MOSI are for programming only.

Answer 1

As Mikael Patel pointed out, my MOSI and MISO pins were switched.

On the pinout for the ATtiny85, the MOSI and MISO pins are for when the chip is a slave (i.e. programming). DO and DI and used for output as SPI master.

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