Mixing
Serial read ok in Putty but not in Python shell
The code I have sends a command to a serial device and returns a string <LF>Mycode<CR> or in Python nMYCODEr is the format I send the command in, I can see the incoming data in putty but not in Python? The incoming data also starts with a <LF> and ends with a <CR>. How do I get this data through to Python?
My code:
import time
import serial
import I2C_LCD_driver
mylcd = I2C_LCD_driver.lcd()
print ("Starting Program")
ser = serial.Serial("/dev/ttyUSB0", baudrate=9600,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS
)
time.sleep(1)
try:
ser.write("nWr".encode('utf-8'))
print ("data echo mode enabled")
while True:
if ser.inWaiting() > 0:
data = ser.readline()
print ("Weight", data.decode(), "kg")
mylcd.lcd_display_string("Weight" + data.decode(), 1)
except KeyboardInterrupt:
print ("Exiting Program")
except:
print ("Error Occurs, Exiting Program")
finally:
ser.close()
pass
python ascii
edited Nov 26 '18 at 1:35
Pang
6,9011664101
asked Nov 20 '18 at 19:24
BradleyBradley
247
add a comment |
The code I have sends a command to a serial device and returns a string <LF>Mycode<CR> or in Python nMYCODEr is the format I send the command in, I can see the incoming data in putty but not in Python? The incoming data also starts with a <LF> and ends with a <CR>. How do I get this data through to Python?
My code:
import time
import serial
import I2C_LCD_driver
mylcd = I2C_LCD_driver.lcd()
print ("Starting Program")
ser = serial.Serial("/dev/ttyUSB0", baudrate=9600,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS
)
time.sleep(1)
try:
ser.write("nWr".encode('utf-8'))
print ("data echo mode enabled")
while True:
if ser.inWaiting() > 0:
data = ser.readline()
print ("Weight", data.decode(), "kg")
mylcd.lcd_display_string("Weight" + data.decode(), 1)
except KeyboardInterrupt:
print ("Exiting Program")
except:
print ("Error Occurs, Exiting Program")
finally:
ser.close()
pass
python ascii
edited Nov 26 '18 at 1:35
Pang
6,9011664101
asked Nov 20 '18 at 19:24
BradleyBradley
247
add a comment |
The code I have sends a command to a serial device and returns a string <LF>Mycode<CR> or in Python nMYCODEr is the format I send the command in, I can see the incoming data in putty but not in Python? The incoming data also starts with a <LF> and ends with a <CR>. How do I get this data through to Python?
My code:
import time
import serial
import I2C_LCD_driver
mylcd = I2C_LCD_driver.lcd()
print ("Starting Program")
ser = serial.Serial("/dev/ttyUSB0", baudrate=9600,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS
)
time.sleep(1)
try:
ser.write("nWr".encode('utf-8'))
print ("data echo mode enabled")
while True:
if ser.inWaiting() > 0:
data = ser.readline()
print ("Weight", data.decode(), "kg")
mylcd.lcd_display_string("Weight" + data.decode(), 1)
except KeyboardInterrupt:
print ("Exiting Program")
except:
print ("Error Occurs, Exiting Program")
finally:
ser.close()
pass
python ascii
edited Nov 26 '18 at 1:35
Pang
6,9011664101
asked Nov 20 '18 at 19:24
BradleyBradley
247
The code I have sends a command to a serial device and returns a string <LF>Mycode<CR> or in Python nMYCODEr is the format I send the command in, I can see the incoming data in putty but not in Python? The incoming data also starts with a <LF> and ends with a <CR>. How do I get this data through to Python?
My code:
import time
import serial
import I2C_LCD_driver
mylcd = I2C_LCD_driver.lcd()
print ("Starting Program")
ser = serial.Serial("/dev/ttyUSB0", baudrate=9600,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS
)
time.sleep(1)
try:
ser.write("nWr".encode('utf-8'))
print ("data echo mode enabled")
while True:
if ser.inWaiting() > 0:
data = ser.readline()
print ("Weight", data.decode(), "kg")
mylcd.lcd_display_string("Weight" + data.decode(), 1)
except KeyboardInterrupt:
print ("Exiting Program")
except:
print ("Error Occurs, Exiting Program")
finally:
ser.close()
pass
python ascii
python ascii
edited Nov 26 '18 at 1:35
Pang
6,9011664101
asked Nov 20 '18 at 19:24
BradleyBradley
247
edited Nov 26 '18 at 1:35
Pang
6,9011664101
asked Nov 20 '18 at 19:24
BradleyBradley
247
edited Nov 26 '18 at 1:35
Pang
6,9011664101
edited Nov 26 '18 at 1:35
Pang
6,9011664101
edited Nov 26 '18 at 1:35
Pang
6,9011664101
6,9011664101
asked Nov 20 '18 at 19:24
BradleyBradley
247
asked Nov 20 '18 at 19:24
BradleyBradley
247
asked Nov 20 '18 at 19:24
BradleyBradley
247
247
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
It looks like the issue is with your call to ser.readline(). The pyserial API states that it uses io.IOBase.readline which reads characters up to the newline (n) character. Since your data begines with n there are no characters before it, and hence the readline call will read zero bytes from the buffer, and return an empty string.
You should either move the n to the end of each message, or use the read(n) call directly to read n bytes from the connection.
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
Does that make it work then? Otherwise I'd say to use the rawread()method and print the data to console to see what you're actually getting.
– jdrd
Nov 20 '18 at 21:02
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
So your string slicing above ([10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end withnand just do a readline, then slice the string after.
– jdrd
Nov 20 '18 at 21:47
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
|
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
It looks like the issue is with your call to ser.readline(). The pyserial API states that it uses io.IOBase.readline which reads characters up to the newline (n) character. Since your data begines with n there are no characters before it, and hence the readline call will read zero bytes from the buffer, and return an empty string.
You should either move the n to the end of each message, or use the read(n) call directly to read n bytes from the connection.
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
Does that make it work then? Otherwise I'd say to use the rawread()method and print the data to console to see what you're actually getting.
– jdrd
Nov 20 '18 at 21:02
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
So your string slicing above ([10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end withnand just do a readline, then slice the string after.
– jdrd
Nov 20 '18 at 21:47
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
|
show 1 more comment
It looks like the issue is with your call to ser.readline(). The pyserial API states that it uses io.IOBase.readline which reads characters up to the newline (n) character. Since your data begines with n there are no characters before it, and hence the readline call will read zero bytes from the buffer, and return an empty string.
You should either move the n to the end of each message, or use the read(n) call directly to read n bytes from the connection.
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
Does that make it work then? Otherwise I'd say to use the rawread()method and print the data to console to see what you're actually getting.
– jdrd
Nov 20 '18 at 21:02
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
So your string slicing above ([10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end withnand just do a readline, then slice the string after.
– jdrd
Nov 20 '18 at 21:47
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
|
show 1 more comment
It looks like the issue is with your call to ser.readline(). The pyserial API states that it uses io.IOBase.readline which reads characters up to the newline (n) character. Since your data begines with n there are no characters before it, and hence the readline call will read zero bytes from the buffer, and return an empty string.
You should either move the n to the end of each message, or use the read(n) call directly to read n bytes from the connection.
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
It looks like the issue is with your call to ser.readline(). The pyserial API states that it uses io.IOBase.readline which reads characters up to the newline (n) character. Since your data begines with n there are no characters before it, and hence the readline call will read zero bytes from the buffer, and return an empty string.
You should either move the n to the end of each message, or use the read(n) call directly to read n bytes from the connection.
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
answered Nov 20 '18 at 19:49
jdrdjdrd
1297
1297
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
Does that make it work then? Otherwise I'd say to use the rawread()method and print the data to console to see what you're actually getting.
– jdrd
Nov 20 '18 at 21:02
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
So your string slicing above ([10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end withnand just do a readline, then slice the string after.
– jdrd
Nov 20 '18 at 21:47
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
|
show 1 more comment
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
Does that make it work then? Otherwise I'd say to use the rawread()method and print the data to console to see what you're actually getting.
– jdrd
Nov 20 '18 at 21:02
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
So your string slicing above ([10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end withnand just do a readline, then slice the string after.
– jdrd
Nov 20 '18 at 21:47
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
I have used the ser.readline(). The incoming data was quite large and most of it unused so I added [10:17] to limit the characters to what I require. ser.readling()[10:17]
– Bradley
Nov 20 '18 at 21:00
Does that make it work then? Otherwise I'd say to use the raw
read() method and print the data to console to see what you're actually getting.– jdrd
Nov 20 '18 at 21:02
Does that make it work then? Otherwise I'd say to use the raw
read() method and print the data to console to see what you're actually getting.– jdrd
Nov 20 '18 at 21:02
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
It works yes, but the update is so slow in python but in putty its instant! I can use the read() but I only want to read 7 of 18 characters any idea how to do this?
– Bradley
Nov 20 '18 at 21:22
So your string slicing above (
[10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end with n and just do a readline, then slice the string after.– jdrd
Nov 20 '18 at 21:47
So your string slicing above (
[10:17]) gives you the characters after the read completes. Putty will display each character individually as it arrives, but with python you decide how often to read and display the data that you receive. If you control the format of the data you receive back you could have each response end with n and just do a readline, then slice the string after.– jdrd
Nov 20 '18 at 21:47
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
That would be the solution but unfortunately the response is preset and can’t be changed
– Bradley
Nov 20 '18 at 21:52
|
show 1 more comment
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