I am trying to use joan's pigpio for python to try to write a command from a rpi3 GPIO pin to a peripheral device. the peripheral device uses UART and when it receives a data packet it will then perform the corresponding function.
example |-----dataBuffer----| start devID size packetCount index futureByte | highByte LowByte | 255 1 2 1 1 0 | 3 195 | |00000011 11000011|
start: beginning of packet
devID: id of device
size: # of command bytes, only one command at a time and each command is 2 bytes so this number is always 2
packetCount: total # of packets in the transmission.(only 1 packet at a time)
index: place of this packet within set of packets
futureByte: not used, keeps the data packet even
dataBuffer: 0 to 16 byte buffer. bc only 1 command is sent at a time, the buffer will only contain 2 bytes(the high byte and the low byte)
peripheral device byte format:
start bit: yes
bit order: 0...7
parity bit: no
baud rate: 9600
I have not yet reached the point where I am actually sending commands to the peripheral. For now I just trying to write on a GPIO using pi.wave_send_once() and verify that this is working correctly using joans piscope and my bench oscope. Here is my script:
` import sys import difflib import pigpio import time import os from os import system system('sudo pigpiod') # GPIO pin constants BAUD = 9600 # 9600 TX = 22 # NOT builtin gpio 14 #create instance of pigpio class pi = pigpio.pi() if not pi.connected: os.system("sudo pigpiod") time.sleep(1) pi = pigpio.pi() pi.set_mode(TX, pigpio.OUTPUT) # set GPIO 14 as an output def send_command(packet): pi.wave_clear() pi.wave_add_serial(TX, BAUD, packet, bb_bits=8) #bb_bits=16 wid = pi.wave_create() pi.wave_send_once(wid) # transmit serial data while pi.wave_tx_busy(): # wait until all data sent pass print('The packet\n{}\n was sent!'.format(packet)) pi.wave_delete(wid) packet = b'3' #packet = b'00000011' #packet = '00000011' send_command(packet) `
Here is the output of the wave_get functions:
control blocks: 14 max cbs: 25016 microseconds: 1146 max micros: 1800000000 pulses: 7 max pulses: 12000
Here is a screenshot of piscope:
As you can see something is wrong. First of all the timing is wrong, at 9600baud each pulse should be 104usec.
- Does anyone have any ideas how to fix the timing problem? I have tried fixing with the core_freq=250 and dtoverlay workarounds I read about, but this did not solve the problem.
- will this method of sending pigpio waves still work for me once I start sending the larger complete packets(64bits)?
- the pigpio library has a function for filtering glitches/noise. Should i be using these? If so i did not really understand how to use them please explain or point to tutorial/example.
script ot send command `
# GPIO pin constants BAUD = 9600 # 9600 TX = 5 #create instance of pigpio class pi = pigpio.pi() if not pi.connected: os.system("sudo pigpiod") time.sleep(1) pi = pigpio.pi() #set mode of tx pin pi.set_mode(TX, pigpio.OUTPUT) # set GPIO 14 as an output # fatal exceptions off (so that closing an unopened gpio doesn't error) pigpio.exceptions = False #pi.bb_serial_read_close(RX) pi.serial_close(TX) # fatal exceptions on pigpio.exceptions = True def wave_dbg(msg): cbs = pi.wave_get_cbs() max_cbs = pi.wave_get_max_cbs() micros = pi.wave_get_micros() max_micros = pi.wave_get_max_micros() pulses = pi.wave_get_pulses() max_pulses = pi.wave_get_max_pulses() print('-------------[DBG - wave]------------------------------') print('-------------[{}]-------------------'.format(msg)) print('control blocks: {} max cbs: {}'.format(cbs,max_cbs)) print('microseconds: {} max micros: {}'.format(micros,max_micros)) print('pulses: {} max pulses: {}'.format(pulses,max_pulses)) print('-------------------------------------------------------') def send_command(packet): print('inside function: {}'.format(type(packet))) print('inside function: {}'.format(packet)) #self.wave_dbg('before wave clear') pi.wave_clear() #self.wave_dbg('after wave clear') pi.wave_add_serial(TX, BAUD, packet, bb_bits = 32) #bb_bits=16 #self.wave_dbg('after serial add') wid = pi.wave_create() #self.wave_dbg('after wave creation') pi.wave_send_once(wid) # transmit serial data #self.wave_dbg('after wave sent') while pi.wave_tx_busy(): # wait until all data sent pass print('The packet\n{}\n was sent!'.format(packet)) pi.wave_delete(wid) wave_dbg('end of function') ''' commands returned from sniffer r_eye_norm = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc3') r_eye_cons = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc5') r_eye_dila = bytearray(b'\xff\x01\x02\x01\x01\x00\x03\xc4') br30 = bytearray(b'\xff\x01\x02\x01\x01\x00\x04d') br_apnea = bytearray(b'\xff\x01\x02\x01\x01\x00\x04`') br5 = bytearray(b'\xff\x01\x02\x01\x01\x00\x04a') ''' r_eye_norm = bytearray(b'\x01\x02\x01\x01\x00\x03\xc3') r_eye_cons = bytearray(b'\x01\x02\x01\x01\x00\x03\xc5') r_eye_dila = bytearray(b'\x01\x02\x01\x01\x00\x03\xc4') br30 = bytearray(b'\x01\x02\x01\x01\x00\x04d') br_apnea = bytearray(b'\x01\x02\x01\x01\x00\x04`') br5 = bytearray(b'\x01\x02\x01\x01\x00\x04a') print(type(br30)) print(br30) send_command(br30) ` 
script for sniffer uart_sniffer.py '
import datetime as dt import time import pigpio
TX = 6 # pin 29 TX_data = [] try: pi = pigpio.pi() # connect to local host #pi.set_mode(RX, pigpio.INPUT) pi.set_mode(TX, pigpio.INPUT) pigpio.exceptions = False pi.bb_serial_read_close(TX) pigpio.exceptions = True #pi.bb_serial_read_open(RX, 9600, 8) pi.bb_serial_read_open(TX, 9600, 8) print('-----------------DATA SOFTWARE SERIAL------------------------') while True: (countTX, dataTX) = pi.bb_serial_read(TX) if countTX: print(dataTX) TX_data.append(dataTX) print('--------------------------------------------------') time.sleep(1) except KeyboardInterrupt: with open('uart_read.txt', 'w') as f: for item in TX_data: f.write('%s\n' % item) pi.bb_serial_read_close(TX) pi.stop() ` 
