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169 | """
A simple example of sending data from 1 nRF24L01 transceiver to another.
This example was written to be used on 2 devices acting as 'nodes'.
See documentation at https://nRF24.github.io/RF24
"""
import time
import struct
from RF24 import RF24, RF24_PA_LOW, RF24_DRIVER
print(__file__) # print example name
########### USER CONFIGURATION ###########
# See https://github.com/TMRh20/RF24/blob/master/pyRF24/readme.md
# Radio CE Pin, CSN Pin, SPI Speed
# CE Pin uses GPIO number with BCM and SPIDEV drivers, other platforms use
# their own pin numbering
# CS Pin addresses the SPI bus number at /dev/spidev<a>.<b>
# ie: RF24 radio(<ce_pin>, <a>*10+<b>); spidev1.0 is 10, spidev1.1 is 11 etc..
CSN_PIN = 0 # GPIO8 aka CE0 on SPI bus 0: /dev/spidev0.0
if RF24_DRIVER == "MRAA":
CE_PIN = 15 # for GPIO22
elif RF24_DRIVER == "wiringPi":
CE_PIN = 3 # for GPIO22
else:
CE_PIN = 22
radio = RF24(CE_PIN, CSN_PIN)
# initialize the nRF24L01 on the spi bus
if not radio.begin():
raise RuntimeError("radio hardware is not responding")
# For this example, we will use different addresses
# An address need to be a buffer protocol object (bytearray)
address = [b"1Node", b"2Node"]
# It is very helpful to think of an address as a path instead of as
# an identifying device destination
# to use different addresses on a pair of radios, we need a variable to
# uniquely identify which address this radio will use to transmit
# 0 uses address[0] to transmit, 1 uses address[1] to transmit
radio_number = bool(
int(input("Which radio is this? Enter '0' or '1'. Defaults to '0' ") or 0)
)
# set the Power Amplifier level to -12 dBm since this test example is
# usually run with nRF24L01 transceivers in close proximity of each other
radio.setPALevel(RF24_PA_LOW) # RF24_PA_MAX is default
# set the TX address of the RX node into the TX pipe
radio.openWritingPipe(address[radio_number]) # always uses pipe 0
# set the RX address of the TX node into a RX pipe
radio.openReadingPipe(1, address[not radio_number]) # using pipe 1
# To save time during transmission, we'll set the payload size to be only
# what we need. A float value occupies 4 bytes in memory using
# struct.pack(); "f" means an unsigned float
radio.payloadSize = struct.calcsize("f")
# for debugging, we have 2 options that print a large block of details
# (smaller) function that prints raw register values
# radio.printDetails()
# (larger) function that prints human readable data
# radio.printPrettyDetails()
# using the python keyword global is bad practice. Instead we'll use a 1 item
# list to store our float number for the payloads sent/received
payload = [0.0]
def master():
"""Transmits an incrementing float every second"""
radio.stopListening() # put radio in TX mode
failures = 0
while failures < 6:
# use struct.pack() to packet your data into the payload
# "<f" means a single little endian (4 byte) float value.
buffer = struct.pack("<f", payload[0])
start_timer = time.monotonic_ns() # start timer
result = radio.write(buffer)
end_timer = time.monotonic_ns() # end timer
if not result:
print("Transmission failed or timed out")
failures += 1
else:
print(
"Transmission successful! Time to Transmit:",
f"{(end_timer - start_timer) / 1000} us. Sent: {payload[0]}",
)
payload[0] += 0.01
time.sleep(1)
print(failures, "failures detected. Leaving TX role.")
def slave(timeout=6):
"""Listen for any payloads and print the transaction
:param int timeout: The number of seconds to wait (with no transmission)
until exiting function.
"""
radio.startListening() # put radio in RX mode
start_timer = time.monotonic()
while (time.monotonic() - start_timer) < timeout:
has_payload, pipe_number = radio.available_pipe()
if has_payload:
# fetch 1 payload from RX FIFO
buffer = radio.read(radio.payloadSize)
# use struct.unpack() to convert the buffer into usable data
# expecting a little endian float, thus the format string "<f"
# buffer[:4] truncates padded 0s in case payloadSize was not set
payload[0] = struct.unpack("<f", buffer[:4])[0]
# print details about the received packet
print(
f"Received {radio.payloadSize} bytes",
f"on pipe {pipe_number}: {payload[0]}",
)
start_timer = time.monotonic() # reset the timeout timer
print("Nothing received in", timeout, "seconds. Leaving RX role")
# recommended behavior is to keep in TX mode while idle
radio.stopListening() # put the radio in TX mode
def set_role() -> bool:
"""Set the role using stdin stream. Timeout arg for slave() can be
specified using a space delimiter (e.g. 'R 10' calls `slave(10)`)
:return:
- True when role is complete & app should continue running.
- False when app should exit
"""
user_input = (
input(
"*** Enter 'R' for receiver role.\n"
"*** Enter 'T' for transmitter role.\n"
"*** Enter 'Q' to quit example.\n"
)
or "?"
)
user_input = user_input.split()
if user_input[0].upper().startswith("R"):
if len(user_input) > 1:
slave(int(user_input[1]))
else:
slave()
return True
if user_input[0].upper().startswith("T"):
master()
return True
if user_input[0].upper().startswith("Q"):
radio.powerDown()
return False
print(user_input[0], "is an unrecognized input. Please try again.")
return set_role()
if __name__ == "__main__":
try:
while set_role():
pass # continue example until 'Q' is entered
except KeyboardInterrupt:
print(" Keyboard Interrupt detected. Powering down radio.")
radio.powerDown()
else:
print(" Run slave() on receiver\n Run master() on transmitter")
|