In the spirit of sharing I wanted to post some code for anyone that wants to play around with SF’s various breakout boards for the rF24L01. I started by buying two of the “Transceiver nRF24L01 Module with RP-SMA” modules (and matching antennas), but then got spooked by having to get both the transmitter and receiver code working at the same time (gee, is the bug on the transmitter side, or the receiver…) So, the modules just sat in my parts box for several months.
However, when the Nordic FOB came out, I got one of those figuring it would cut down my learning curve quite a bit to start with a working transmitter. Since I don’t have an Atmel programmer, I took the sample receiver code SF provided and reworked it a bit for the PIC16F610 (using the CCS “PCM” C compiler and MPLAB), which I’ll share here:
#device PIC16F610
#fuses PUT, IOSC8, INTRC_IO, NOWDT, NOPROTECT, BROWNOUT, NOMCLR
#use delay(clock=8000000)
#byte PORTA = 0x05
#byte TRISA = 0x85
#byte PORTC = 0x07
#byte TRISC = 0x87
#byte ANSEL = 0x91
#bit RX_CE = PORTA.0 // out Pin 13
#bit RX_CSN = PORTA.1 // out Pin 12
#bit RX_SCK = PORTA.2 // out Pin 11
#bit RX_MISO = PORTA.3 // in Pin 4
#bit RX_MOSI = PORTA.4 // out Pin 3
char data[4];
char spiIO (char out) {
char ii, in;
in = 0;
for(ii = 0 ; ii < 8 ; ii++) {
if ((out & 0x80) != 0) {
RX_MOSI = 1;
} else {
RX_MOSI = 0;
}
RX_SCK = 1;
delay_us(5);
in <<= 1;
if (RX_MISO != 0) {
in |= 0x01;
}
RX_SCK = 0;
delay_us(5);
out <<= 1;
}
return in;
}
char sendCmd (char cmd, char data) {
char status;
RX_CE = 0; // Stand by mode
RX_CSN = 0; // Select chip
spiIO(cmd);
status = spiIO(data);
RX_CSN = 1; // Deselect chip
return status ;
}
void initRcvr (void) {
char ii;
RX_CE = 0; // Go into standby mode
sendCmd(0x20, 0x39); // Enable RX IRQ, CRC Enabled, be a receiver
sendCmd(0x21, 0x00); // Disable auto-acknowledge
sendCmd(0x23, 0x03); // Set address width to 5bytes (default, not really needed)
sendCmd(0x26, 0x07); // Air data rate 1Mbit, 0dBm, Setup LNA
sendCmd(0x31, 0x04); // 4 byte receive payload
sendCmd(0x25, 0x02); // RF Channel 2 (default, not really needed)
RX_CSN = 0; // Select chip
spiIO(0x2A);
for (ii = 0 ; ii < 4 ; ii++) {
spiIO(0xE7);
}
RX_CSN = 1; // Deselect chip
sendCmd(0x20, 0x3B); // RX interrupt, power up, be a receiver
RX_CE = 1; // Start receiving
}
char sendByte (char cmd) {
char status;
RX_CSN = 0; // Select chip
status = spiIO(cmd);
RX_CSN = 1; // Deselect chip
return status;
}
void receive (void) {
char ii;
RX_CSN = 0; // Stand by mode
spiIO(0x61); // Read RX Payload
for (ii = 0; ii < 4; ii++) {
data[ii] = spiIO(0xFF);
}
RX_CSN = 1;
sendByte(0xE2); // Flush RX FIFO
sendCmd(0x27, 0x40); // Clear RF FIFO interrupt
RX_CE = 1; // Go back to receiving!
}
int main (void) {
char leds;
TRISA = 0x08; // PORTA.0-3,5 are outputs, PORTA.4 is input
TRISC = 0x00; // PORTC.0-5 are outputs
ANSEL = 0x00; // All inputs digital
PORTC = 0x18;
RX_CE = 0; // Stand by mode
initRcvr();
leds = 0x18;
while(1) {
char in;
in = sendByte(0xFF); //Get status register
if ((in & 0x40) != 0) {
receive();
switch (data[0]) {
case 0x17: // Left button
leds ^= 0x01;
break;
case 0x1D: // Top button
leds ^= 0x02;
break;
case 0x1B: // Right button
leds ^= 0x04;
break;
case 0x1E: // Bottom button
leds ^= 0x08;
break;
case 0x0F: // Center button
leds ^= 0x10;
break;
}
PORTC = leds;
}
}
}
The code toggles LEDs attached to port C on the 610 in response to button presses on the FOB. See the #bit definitions at the top of the source to see how the various signals from the rF24L01 are wired to the 16F610.
Once I had the receiver working, I coded up a simple, one button transmitter using a PIC12F683 that mimics what the FOB does. That code is here:
#device PIC12F683
#fuses PUT, INTRC_IO, NOWDT, NOPROTECT, BROWNOUT, NOMCLR
#use delay(clock=8000000)
#byte GPIO = 0x05
#byte OPTION = 0x81
#byte TRISIO = 0x85
#byte OSCCON = 0x8F
#byte WPU = 0x95
#bit GPPU = OPTION.7
#bit TX_CE = GPIO.0 // out Pin 7
#bit TX_CSN = GPIO.1 // out Pin 6
#bit TX_SCK = GPIO.2 // out Pin 5
#bit TX_MISO = GPIO.3 // in Pin 4
#bit TX_MOSI = GPIO.4 // out Pin 3
#bit BUTTON = GPIO.5 // in Pin 2
char data[4];
char spiIO (char out) {
char ii, in;
in = 0;
for(ii = 0 ; ii < 8 ; ii++) {
if ((out & 0x80) != 0) {
TX_MOSI = 1;
} else {
TX_MOSI = 0;
}
TX_SCK = 1;
in <<= 1;
if (TX_MISO != 0) {
in |= 0x01;
}
TX_SCK = 0;
out <<= 1;
}
return in;
}
char sendCmd (char cmd, char data) {
char status;
TX_CE = 0; // Stand by mode
TX_CSN = 0; // Select chip
spiIO(cmd);
status = spiIO(data);
TX_CSN = 1; // Deselect chip
return status ;
}
char sendByte (char cmd) {
char status;
TX_CSN = 0; // Select chip
status = spiIO(cmd);
TX_CSN = 1; // Deselect chip
return status;
}
void initXmtr (void) {
char ii;
TX_CE = 0; // Go into standby mode
sendCmd(0x20, 0x78); // CRC Enabled, be a transmitter
sendCmd(0x21, 0x00); // Disable auto-acknowledge
sendCmd(0x24, 0x00); // Disable auto-retransmit
sendCmd(0x23, 0x03); // Set address width to 5bytes (default, not really needed)
sendCmd(0x26, 0x07); // Air data rate 1Mbit, 0dBm, Setup LNA
sendCmd(0x25, 0x02); // RF Channel 2 (default, not really needed)
TX_CSN = 0; // Select chip
spiIO(0x30); // Set TX Address
for (ii = 0 ; ii < 4 ; ii++) {
spiIO(0xE7);
}
TX_CSN = 1; // Deselect chip
sendCmd(0x20, 0x7A); // Power up transmitter
sendByte(0xFF);
}
void xmit (void) {
char ii;
sendCmd(0x27, 0x7E); // Clear any interrupts
sendCmd(0x20, 0x7A); // Power up transmitter
sendByte(0xE1); // Clear TX FIFO
TX_CSN = 0; // Select chip
spiIO(0xA0); // Clock in 4 byte data payload
for (ii = 0 ; ii < 4 ; ii++) {
spiIO(data[ii]);
}
TX_CSN = 1; // Deselect chip
TX_CE = 1; // Pulse CE to start transmission
delay_us(3);
TX_CE = 0;
}
int main (void) {
char bc, bo;
OSCCON = 0x70; // 8 Mhz
while ((OSCCON & 0x04) == 0)
;
TRISIO = 0x28; // GPIO.0-2,4 are outputs, GPIO.3,5 are inputs
WPU = 0x20; // Weak pullup on GPIO.5
GPPU = 0; // Enable global pullup enable
TX_CE = 0; // Standby mode
bo = 0xFF;
initXmtr();
while(1) {
bc = GPIO;
if (((bc ^ bo) & 0x20) != 0 && (bc & 0x20) == 0) {
// get here on button transition from unpressed to pressed
data[0] = 0x0F; // Send "Center" button code to receiver
data[1] = 0;
data[2] = 0;
data[3] = 0;
xmit();
}
bo = bc;
delay_us(100);
}
}
My goal in coding these was to create simple examples that someone could use as a starting point to get something working with a minimum of components before branching out into more complex propjects. So, let me know if this is useful. Thanks.
Wayne
