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Allow access to RadioHead packet headers #12

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Merged
merged 4 commits into from
Nov 19, 2018
Merged

Allow access to RadioHead packet headers #12

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b89c522
add access to RH packet header
jerryneedell Nov 18, 2018
1adfb73
cleanup - add assert for rx_filter
jerryneedell Nov 18, 2018
c096b11
revise rx_filter handling
jerryneedell Nov 19, 2018
af1a916
update comments
jerryneedell Nov 19, 2018
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50 changes: 34 additions & 16 deletions adafruit_rfm69.py
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Original file line number Diff line number Diff line change
Expand Up @@ -674,11 +674,14 @@ def frequency_deviation(self, val):
self._write_u8(_REG_FDEV_MSB, fdev >> 8)
self._write_u8(_REG_FDEV_LSB, fdev & 0xFF)

def send(self, data, timeout=2.):
def send(self, data, timeout=2.,
tx_header=(_RH_BROADCAST_ADDRESS, _RH_BROADCAST_ADDRESS, 0, 0)):
"""Send a string of data using the transmitter.
You can only send 60 bytes at a time
(limited by chip's FIFO size and appended headers).
Note this appends a 4 byte header to be compatible with the RadioHead library.
This appends a 4 byte header to be compatible with the RadioHead library.
The tx_header defaults to using the Broadcast addresses. It may be overidden
by specifying a 4-tuple of bytes containing (To,From,ID,Flags)
The timeout is just to prevent a hang (arbitrarily set to 2 seconds)
"""
# Disable pylint warning to not use length as a check for zero.
Expand All @@ -687,6 +690,7 @@ def send(self, data, timeout=2.):
# buffer be within an expected range of bounds. Disable this check.
# pylint: disable=len-as-condition
assert 0 < len(data) <= 60
assert len(tx_header) == 4, "tx header must be 4-tuple (To,From,ID,Flags)"
# pylint: enable=len-as-condition
self.idle() # Stop receiving to clear FIFO and keep it clear.
# Fill the FIFO with a packet to send.
Expand All @@ -697,10 +701,10 @@ def send(self, data, timeout=2.):
# Add 4 bytes of headers to match RadioHead library.
# Just use the defaults for global broadcast to all receivers
# for now.
self._BUFFER[2] = _RH_BROADCAST_ADDRESS # txHeaderTo
self._BUFFER[3] = _RH_BROADCAST_ADDRESS # txHeaderFrom
self._BUFFER[4] = 0 # txHeaderId
self._BUFFER[5] = 0 # txHeaderFlags
self._BUFFER[2] = tx_header[0] # Header: To
self._BUFFER[3] = tx_header[1] # Header: From
self._BUFFER[4] = tx_header[2] # Header: Id
self._BUFFER[5] = tx_header[3] # Header: Flags
device.write(self._BUFFER, end=6)
# Now send the payload.
device.write(data)
Expand All @@ -718,14 +722,27 @@ def send(self, data, timeout=2.):
if timed_out:
raise RuntimeError('Timeout during packet send')

def receive(self, timeout=0.5, keep_listening=True):
def receive(self, timeout=0.5, keep_listening=True, with_header=False,
rx_filter=_RH_BROADCAST_ADDRESS):
"""Wait to receive a packet from the receiver. Will wait for up to timeout_s amount of
seconds for a packet to be received and decoded. If a packet is found the payload bytes
are returned, otherwise None is returned (which indicates the timeout elapsed with no
reception). Note this assumes a 4-byte header is prepended to the data for compatibilty
with the RadioHead library (the header is not validated nor returned). If keep_listening
is True (the default) the chip will immediately enter listening mode after reception of
a packet, otherwise it will fall back to idle mode and ignore any future reception.
reception).
If keep_listening is True (the default) the chip will immediately enter listening mode
after reception of a packet, otherwise it will fall back to idle mode and ignore any
future reception.
A 4-byte header must be prepended to the data for compatibilty with the
RadioHead library.
The header consists of a 4 bytes (To,From,ID,Flags). The default setting will accept
any incomming packet and strip the header before returning the packet to the caller.
If with_header is True then the 4 byte header will be returned with the packet.
The payload then begins at packet[4].
rx_fliter may be set to reject any "non-broadcast" packets that do not contain the
specfied "To" value in the header.
if rx_filter is set to 0xff (_RH_BROADCAST_ADDRESS) or if the "To" field (packet[[0])
is equal to 0xff then the packet will be accepted and returned to the caller.
If rx_filter is not 0xff and packet[0] does not match rx_filter then
the packet is ignored and None is returned.
"""
# Make sure we are listening for packets.
self.listen()
Expand Down Expand Up @@ -760,13 +777,14 @@ def receive(self, timeout=0.5, keep_listening=True):
device.readinto(self._BUFFER, end=fifo_length)
packet = None
else:
# Read the 4 bytes of the RadioHead header.
device.readinto(self._BUFFER, end=4)
# Ignore validating any of the header bytes.
# Now read the remaining packet payload as the result.
fifo_length -= 4
packet = bytearray(fifo_length)
device.readinto(packet)
if (rx_filter != _RH_BROADCAST_ADDRESS and packet[0] != _RH_BROADCAST_ADDRESS
and packet[0] != rx_filter):
packet = None
if not with_header: # skip the header if not wanted
packet = packet[4:]

# Listen again if necessary and return the result packet.
if keep_listening:
self.listen()
Expand Down