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Sped up for the RaspberryPi SPI

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Tested writing 437 bytes of data to an NTAG215.
Original script: 18.9 seconds write, 19.2 seconds read.
Modified script: 7.6 seconds write, 7.8 seconds read.
This commit is contained in:
tgikal 2019-06-28 15:12:41 -04:00 committed by GitHub
parent 949a5c6213
commit c44abc207e
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 10 additions and 15 deletions
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25
adafruit_pn532/spi.py
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@ -51,12 +51,7 @@ _SPI_READY = const(0x01)
def reverse_bit(num):
"""Turn an LSB byte to an MSB byte, and vice versa. Used for SPI as
it is LSB for the PN532, but 99% of SPI implementations are MSB only!"""
result = 0
for _ in range(8):
result <<= 1
result += (num & 1)
num >>= 1
return result
return int('{:08b}'.format(num)[::-1], 2)
class PN532_SPI(PN532):
"""Driver for the PN532 connected over SPI. Pass in a hardware or bitbang
@ -83,12 +78,12 @@ class PN532_SPI(PN532):
timestamp = time.monotonic()
while (time.monotonic() - timestamp) < timeout:
with self._spi as spi:
time.sleep(0.02) # required
#time.sleep(0.02) # required
spi.write_readinto(status, status) #pylint: disable=no-member
if reverse_bit(status[1]) == 0x01: # LSB data is read in MSB
return True # Not busy anymore!
else:
time.sleep(0.01) # pause a bit till we ask again
#else:
# time.sleep(0.01) # pause a bit till we ask again
# We timed out!
return False
@ -100,12 +95,12 @@ class PN532_SPI(PN532):
frame[0] = reverse_bit(_SPI_DATAREAD)
with self._spi as spi:
time.sleep(0.02) # required
#time.sleep(0.02) # required
spi.write_readinto(frame, frame) #pylint: disable=no-member
for i, val in enumerate(frame):
frame[i] = reverse_bit(val) # turn LSB data to MSB
if self.debug:
print("Reading: ", [hex(i) for i in frame[1:]])
#if self.debug:
# print("Reading: ", [hex(i) for i in frame[1:]])
return frame[1:]
def _write_data(self, framebytes):
@ -113,8 +108,8 @@ class PN532_SPI(PN532):
# start by making a frame with data write in front,
# then rest of bytes, and LSBify it
rev_frame = [reverse_bit(x) for x in bytes([_SPI_DATAWRITE]) + framebytes]
if self.debug:
print("Writing: ", [hex(i) for i in rev_frame])
#if self.debug:
# print("Writing: ", [hex(i) for i in rev_frame])
with self._spi as spi:
time.sleep(0.02) # required
#time.sleep(0.02) # required
spi.write(bytes(rev_frame)) #pylint: disable=no-member