arduino-c/rf24/rf24.c

#include "rf24.h"
#include "nRF24L01.h"
#include "../ard/pins.h"

// FIXME for testing, remove later
#include <util/delay.h>

#define CONFIG_CRC (1<<EN_CRC)|(1<<CRCO)

unsigned char _ce, _csn, _sck, _mo, _mi, _irq, _payload_len;

void rf24_rx();
void rf24_tx();
unsigned char rf24_fifo_empty();
void rf24_serial_transmit(unsigned char*, unsigned char);
unsigned char rf24_serial_write(unsigned char);

void rf24_init(unsigned char ce, unsigned char csn, unsigned char sck, unsigned char mo, unsigned char mi, unsigned char irq){
	pin_mode(ce, OUTPUT);
	digital_write(ce, LOW); // disable
	pin_mode(csn, OUTPUT);
	digital_write(csn, HIGH); // disable
	pin_mode(sck, OUTPUT);
	pin_mode(mo, OUTPUT);
	pin_mode(mi, INPUT);
	pin_mode(irq, OUTPUT);

	_ce = ce;
	_csn = csn;
	_sck = sck;
	_mo = mo;
	_mi = mi;
	_irq = irq;
}

// channel in 1Mhz steps
void rf24_config(unsigned char channel, unsigned char payload_len){
	_payload_len = payload_len;

	rf24_config_register(RF_CH, channel&RF_CH_MASK); // 2.4Ghz + channel*1Mhz

	rf24_config_register(RX_PW_P0, 0x00); // auto ACK
	rf24_config_register(RX_PW_P1, payload_len&RX_PW_MASK); // data
	rf24_config_register(RX_PW_P2, 0x00); // unused...
	rf24_config_register(RX_PW_P3, 0x00);
	rf24_config_register(RX_PW_P4, 0x00);
	rf24_config_register(RX_PW_P5, 0x00);

	// low transmission rate, 0dBm
	rf24_config_register(RF_SETUP, (0<<RF_DR_LOW)|(0x03<<RF_PWR));

	// CRC
	rf24_config_register(CONFIG, CONFIG_CRC);

	// auto ACK for pipe 0 and 1 (disable the rest of them)
	rf24_config_register(EN_AA, (1<<ENAA_P0)|(1<<ENAA_P1)|(0<<ENAA_P2)|(0<<ENAA_P3)|(0<<ENAA_P4)|(0<<ENAA_P5));

	// rx address
	rf24_config_register(EN_RXADDR, (1<<ERX_P0)|(1<<ERX_P1)|(0<<ERX_P2)|(0<<ERX_P3)|(0<<ERX_P4)|(0<<ERX_P5));

	// auto retransmit, 1000us, 15 retransmits
	rf24_config_register(SETUP_RETR, (0x04<<ARD)|(0x0F<<ARC));

	// fixed package length
	rf24_config_register(DYNPD, 0x00);

	rf24_rx();
}

void rf24_rx_addr(unsigned char* addr){
	digital_write(_csn, LOW);
	rf24_serial_write(W_REGISTER|RX_ADDR_P1); // data pipe
	rf24_serial_transmit(addr, 5);
	digital_write(_csn, HIGH);
}

void rf24_tx_addr(unsigned char* addr){
	digital_write(_csn, LOW);
	rf24_serial_write(W_REGISTER|RX_ADDR_P0); // auto ACK pipe address must match...
	rf24_serial_transmit(addr, 5);
	rf24_serial_write(W_REGISTER|TX_ADDR); // tx address
	rf24_serial_transmit(addr, 5);
	digital_write(_csn, HIGH);
}

void rf24_rx(){
	digital_write(_csn, LOW);
	rf24_serial_write(FLUSH_RX);
	digital_write(_csn, HIGH);

	digital_write(_ce, LOW);
	rf24_config_register(STATUS, (1<<RX_DR)|(1<<TX_DS)|(1<<MAX_RT));
	rf24_config_register(CONFIG, CONFIG_CRC|(1<<PWR_UP)|(1<<PRIM_RX));
	digital_write(_ce, HIGH);
}

void rf24_tx(){
	digital_write(_ce, LOW);
	rf24_config_register(STATUS, (1<<RX_DR)|(1<<TX_DS)|(1<<MAX_RT));
	rf24_config_register(CONFIG, CONFIG_CRC|(1<<PWR_UP)|(0<<PRIM_RX));
}

void rf24_power_down(){
	digital_write(_ce, LOW);
	rf24_config_register(CONFIG, CONFIG_CRC);
}

void rf24_send(unsigned char* data){
	rf24_tx();
	digital_write(_csn, LOW);
	rf24_serial_write(FLUSH_TX);
	rf24_serial_write(W_TX_PAYLOAD);
	rf24_serial_transmit(data, _payload_len);
	digital_write(_csn, HIGH);
	digital_write(_ce, HIGH);
}

unsigned char rf24_is_sending(){
	unsigned char status = rf24_status();
	return !(status&((1<<TX_DS)|(1<<MAX_RT)));
}

unsigned char rf24_data_ready(){
	unsigned char status = rf24_status();

	if(status&(1<<RX_DR)){
		return 1;
	}

	return !rf24_fifo_empty();
}

void rf24_get_data(unsigned char* data){
	digital_write(_csn, LOW);
	rf24_serial_write(R_RX_PAYLOAD);
	unsigned char i = 0;

	for(i = 0; i < 4; i++){
		data[i] = rf24_serial_write(NOP);
	}

	rf24_serial_write(FLUSH_RX);
	digital_write(_csn, HIGH);
	rf24_config_register(STATUS, 1<<RX_DR);
}

unsigned char rf24_status(){
	digital_write(_csn, LOW);
	unsigned char status = rf24_serial_write(NOP); // returns STATUS register
	digital_write(_csn, HIGH);
	return status;
}

void rf24_config_register(unsigned char reg, unsigned char value){
	digital_write(_csn, LOW);
	rf24_serial_write(W_REGISTER|(reg&REG_MASK));
	rf24_serial_write(value);
	digital_write(_csn, HIGH);
}

unsigned char rf24_read_register(unsigned char reg){
	digital_write(_csn, LOW);
	rf24_serial_write(R_REGISTER|(reg&REG_MASK));
	unsigned char data = rf24_serial_write(NOP);
	digital_write(_csn, HIGH);
	return data;
}

unsigned char rf24_fifo_empty(){
	unsigned char fifo = rf24_read_register(FIFO_STATUS);
	return fifo&(1<<RX_EMPTY);
}

void rf24_serial_transmit(unsigned char* data, unsigned char len){
	unsigned char i = 0;

	for(i = 0; i < len; i++){
		rf24_serial_write(data[i]);
	}
}

unsigned char rf24_serial_write(unsigned char data){
	digital_write(_sck, LOW); // clock
	unsigned char i = 0, rx = 0;

	_delay_ms(40); // FIXME remove

	for(i = 0; i < 8; i++){
		_delay_ms(5); // FIXME remove

		// write bit
		if(data&(1<<(7-i))){
			digital_write(_mo, HIGH);
		}
		else{
			digital_write(_mo, LOW);
		}

		// read bit
		digital_write(_sck, HIGH);
		rx = rx<<1;

		if(digital_read(_mi)){
			rx |= 0x01;
		}

		digital_write(_sck, LOW);
	}

	_delay_ms(5); // FIXME remove
	digital_write(_mo, LOW);

	return rx;
}