Berikut adalah beberapa Python yang saya gunakan untuk menguji keandalan serial perangkat lunak. Sisi inputnya cukup sepele. Anda cukup membuat panggilan terbuka serial bit bit yang sesuai dengan Python atau C. Sisi output lebih terlibat karena Anda harus menggunakan bentuk gelombang untuk membangun bit stream.
Kode di sini menggunakan data 7-bit daripada 8-bit. Tes ditulis pada waktu yang hampir bersamaan ketika saya menambahkan dukungan untuk bit yang berbeda per byte.
Kode menulis blok data biner ke gpio yang terhubung ke laptop (melalui dongle serial). Laptop menggemakan data serial yang masuk ke garis seri keluarannya. Pi membaca data serial di gpio lain.
Kode memeriksa perbedaan antara data yang dikirim dan diterima. Laptop diasumsikan bebas kesalahan, jadi setiap kesalahan diasumsikan berada dalam bit banging.
Melihat log apa pun yang kurang dari 19.2kbps solid. Apa pun hingga 115.2kbps masuk akal (tetapi akan membutuhkan checksumming) dan 230.4kbps memberikan tingkat kesalahan 13% byte.
#!/usr/bin/env python
# bb_serial.py
# 2014-12-23
# Public Domain
# bit bang transmit and receive of serial data
#
# tested by connecting the arbitrary RX/TX gpios to a USB
# serial dongle plugged in to a Linux box.
#
# on the Linux box set the baud and data bits (cs5-cs8)
#
# stty -F /dev/ttyUSB0 19200 cs8
# cat </dev/ttyUSB0 >/dev/ttyUSB0
#
# so the Linux box echoes back data received from the Pi.
#
# laptop timings deviations
#
# baud exp us act us
# 50 20000 13310 * 75
# 75 13333 13310
# 110 9091 13310 * 75
# 134 7462 6792 * 150
# 150 6667 6792
# 200 5000 6792 * 150
# 300 3333 3362
#
import sys
import time
import difflib
import pigpio
RX=19
TX=26
MSGLEN=256
if len(sys.argv) > 1:
baud = int(sys.argv[1])
else:
baud = 115200
if len(sys.argv) > 2:
bits = int(sys.argv[2])
else:
bits = 8
if len(sys.argv) > 3:
runtime = int(sys.argv[3])
else:
runtime = 300
ten_char_time = 100.0 / float(baud)
if ten_char_time < 0.1:
ten_char_time = 0.1
MASK=(1<<bits)-1
# initialise test data
msg = [0] * (MSGLEN+256)
for i in range(len(msg)):
msg[i] = i & MASK
first = 0
pi = pigpio.pi()
pi.set_mode(TX, pigpio.OUTPUT)
# fatal exceptions off (so that closing an unopened gpio doesn't error)
pigpio.exceptions = False
pi.bb_serial_read_close(RX)
# fatal exceptions on
pigpio.exceptions = True
# create a waveform representing the serial data
pi.wave_clear()
TEXT=msg[first:first+MSGLEN]
pi.wave_add_serial(TX, baud, TEXT)
wid=pi.wave_create()
# open a gpio to bit bang read the echoed data
pi.bb_serial_read_open(RX, baud, bits)
# zero error counts
bad_char = 0
total_char = 0
# run for fixed time
start=time.time()
while (time.time()-start) < runtime:
pi.wave_send_once(wid) # transmit serial data
pi.wave_delete(wid)
TXTEXT = TEXT
first += 1
if first >= MSGLEN:
first = 0
TEXT=msg[first:first+MSGLEN]
pi.wave_add_serial(TX, baud, TEXT,bb_bits=7)
while pi.wave_tx_busy(): # wait until all data sent
pass
wid=pi.wave_create()
count = 1
text=""
lt = 0
total_char += MSGLEN
while count: # read echoed serial data
(count, data) = pi.bb_serial_read(RX)
if count:
text += data
lt += count
time.sleep(ten_char_time) # enough time to ensure more data
if text != TXTEXT: # Do sent and received match?
if lt == MSGLEN: # No, is message correct length?
for i in range(MSGLEN): # If so compare byte by byte.
if text[i] != TXTEXT[i]:
# print("{:2X} {:2X}".format(text[i], TXTEXT[i]))
bad_char += 1
else: # Wrong message length, find matching blocks.
ok = 0
s=difflib.SequenceMatcher(None, TXTEXT, text)
for frag in s.get_matching_blocks():
ok += frag[2] # More matching bytes found.
# print(frag)
# print(text, MSGLEN, ok)
if ok < MSGLEN: # Sanity check.
bad_char += (MSGLEN - ok)
else:
print("*** ERRONEOUS good={} LEN={} ***".format(ok, MSGLEN))
print("secs={} baud={} bits={} bad={:.3f}%".
format(runtime, baud, bits, float(bad_char)*100.0/float(total_char)))
print("total={} badchar={}".format(total_char, bad_char))
# free resources
pi.wave_delete(wid)
pi.bb_serial_read_close(RX)
pi.stop()
Log
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 230400; done
secs=300 baud=230400 bad=12.610%
total=249344 badchar=31443
secs=300 baud=230400 bad=12.580%
total=247296 badchar=31111
secs=300 baud=230400 bad=12.669%
total=246528 badchar=31232
secs=300 baud=230400 bad=12.274%
total=249600 badchar=30635
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 115200; done
secs=300 baud=115200 bad=0.378%
total=246784 badchar=934
secs=300 baud=115200 bad=0.152%
total=241408 badchar=368
secs=300 baud=115200 bad=0.189%
total=249088 badchar=472
secs=300 baud=115200 bad=0.347%
total=242688 badchar=843
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 57600; done
secs=300 baud=57600 bad=0.080%
total=220416 badchar=177
secs=300 baud=57600 bad=0.066%
total=219392 badchar=145
secs=300 baud=57600 bad=0.099%
total=219904 badchar=218
secs=300 baud=57600 bad=0.084%
total=219136 badchar=184
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 38400; done
secs=300 baud=38400 bad=0.019%
total=206336 badchar=39
secs=300 baud=38400 bad=0.021%
total=206848 badchar=43
secs=300 baud=38400 bad=0.015%
total=206592 badchar=30
secs=300 baud=38400 bad=0.030%
total=206592 badchar=61
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 19200; done
secs=300 baud=19200 bad=0.000%
total=175104 badchar=0
secs=300 baud=19200 bad=0.000%
total=175360 badchar=0
secs=300 baud=19200 bad=0.000%
total=175360 badchar=0
secs=300 baud=19200 bad=0.000%
total=174336 badchar=0
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 75; done
secs=300 baud=75 bad=0.000%
total=2048 badchar=0
secs=300 baud=75 bad=0.000%
total=2048 badchar=0
secs=300 baud=75 bad=0.000%
total=2048 badchar=0
secs=300 baud=75 bad=0.000%
total=2048 badchar=0
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 19200; done
secs=300 baud=19200 bad=0.000%
total=174592 badchar=0
secs=300 baud=19200 bad=0.000%
total=174592 badchar=0
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 19200; done
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
secs=300 baud=19200 bad=0.000%
total=175360 badchar=0
secs=300 baud=19200 bad=0.000%
total=174592 badchar=0
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 19200; done
secs=300 baud=19200 bad=0.000%
total=174592 badchar=0
secs=300 baud=19200 bad=0.000%
total=175104 badchar=0
secs=300 baud=19200 bad=0.000%
total=175104 badchar=0
secs=300 baud=19200 bad=0.000%
total=175360 badchar=0
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 19200; done
secs=300 baud=19200 bad=0.000%
total=175104 badchar=0
secs=300 baud=19200 bad=0.000%
total=174592 badchar=0
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
secs=300 baud=19200 bad=0.000%
total=175104 badchar=0
harry /ram $ for ((i=0;i<4;i++)); do /code/bb_serial.py 19200; done
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
secs=300 baud=19200 bad=0.000%
total=174848 badchar=0
secs=300 baud=19200 bad=0.000%
total=175104 badchar=0