Serial monitor EOL and send_on_enter filter not working properly

[schleb]

Issue:

• Serial monitor sends no EOL bytes with send_on_enter filter enabled (CR and/or LF bytes are missing at line end)
• Send-on_enter does not work at all with EOL set to CR or EOL set to LF. It only sends the line if EOL is set to CRLF

Complete description:
I have a simple setup in which an ESP32 microcontroller replies the bytes sent to it via serial port. It replys the bytes in decimal representation so that I can read them easily:

Code:

void loop()
{
   int byte;

   if (Serial.available())
   {
    byte = Serial.read();

    Serial.print("received:");
    Serial.println(byte, DEC);
  }
}

Monitor snap (of typing [a] [Enter] [b] [Enter] [c] [Enter])

a
received:97
b
received:98
c
received:99

The issue is as you can see easily: there is no CR or LF or CRLF sent by the monitor. If I use another Terminal it works. E.g. with Arduino IDE I receive LF (dec 10). The Arduino IDE has no echo of the sent bytes, so sending the same bytes (a, b, c) it looks like this:

received:97
received:10
received:98
received:10
received:99
received:10

The EOL parameter of the monitor is set to CRLF (default). If I change the EOL parameter of the monitor to CR or LF, the send_on_enter filter does not work. Nothing is beeing sent. If I then change the parameter back to CRLF odd things happen - it sends out all the old stuff with CR(13) or LF(10):

a
received:97
b
received:98
c
received:99
--- EOL: CR ---
a
b
c
--- EOL: LF ---
a
b
c
--- EOL: CRLF ---
a
received:97
received:13
received:98
received:13
received:99
received:13
received:97
received:10
received:98
received:10
received:99
received:10
received:97
b
received:98
c
received:99

Platformio.ini:
monitor_speed = 115200
monitor_flags=
--echo
monitor_filters=
send_on_enter

System:
PIO Core 5.0.3 Home 3.3.1
VS Code 1.52.0
Windows 10

The issue seems to be happened also to this guy: https://community.platformio.org/t/monitor-send-on-enter-filter-not-work-with-eol-lf/17356

[ivankravets]

Thanks for the report!

Please re-test with pio upgrade --dev.

[niclasku]

This fix does not work for me. platformio/commands/device/filters/send_on_enter.py seems to remove the EOL from the buffer after it gets appended a few lines above. Changing the method to this works for me:

def tx(self, text):
  self._buffer += text
  if self._buffer.endswith(self._eol):
    return self._buffer
  return ""

Not sure if this hack has any side effects.

[ivankravets]

This is the correct behavior. We send text ON ENTER and we don't send "enter". If you need EOL chars - then do not use this filter.

@schleb Am I correct?

[niclasku]

I wonder how I could send something like command parameter\r\n then. With defaults it would send c\r\n, o\r\n, m\r\n and so on. I would expect that if send_on_enter is enabled it sends command parameter with no --eol specified, command parameter\r with -eol=CR and command paramter\r\n with --eol=CRLF.

Same problem is mentioned here: Forum

[ivankravets]

Thanks for the report! Please re-test with pio upgrade --dev.

[niclasku]

Thank you very much for the fast response! This works pretty well for me, but I am not sure if there exists a use case where you want to use send_on_enter with no EOL chars at all. If you don't use the --eol flag it currently defaults to CRLF and there seems to be no option to disable sending of EOL chars if send_on_enter is enabled. Supporting for example --eol=None could help people in this situation.

[ivankravets]

PySerial does not support this https://github.com/pyserial/pyserial/blob/master/serial/tools/miniterm.py#L902

[schleb]

@ivankravets

This is the correct behavior. We send text ON ENTER and we don't send "enter". If you need EOL chars - then do not use this filter.

@schleb Am I correct?

Mh, I also expected the EOL characters to be sent while send_on_enter is enabled. So the fix also did not work for me as I expected.

@niclasku

Thank you very much for the fast response! This works pretty well for me, but I am not sure if there exists a use case where you want to use send_on_enter with no EOL chars at all. If you don't use the --eol flag it currently defaults to CRLF and there seems to be no option to disable sending of EOL chars if send_on_enter is enabled. Supporting for example --eol=None could help people in this situation.

That's an interesting question :-) I would have said no, but indeed I just had this use case one week ago as I had to communicate with a matchbox laser module (https://integratedoptics.com/) which has a weird communication protocol. In order to send a command you have to send all command-bytes in a very short timing without EOL. The laser accepts the command in the moment that no further bytes follow. That is not possible by typing the command by hand in a terminal because after each byte you type the laser thinks the command is complete - and says "error" because the command is not complete. So here you need the possibility to send a complete line without EOL.

I agree: It would be nice to have all options: sending CR, LF, CRLF and none

[MrtnCttn]

Hello,

Has anyone found a way to send a configurable EOL character with the send_on_enter filter?

I have reproduced basically the same steps as schleb. Using an Arduino Nano board, VSCode 1.63.2, python 3.10.1, macOS 12.0.1. Same code for troubleshooting:

void loop()
{
   int byte;
   if (Serial.available())
   {
    byte = Serial.read();
    Serial.print("received:");
    Serial.println(byte, DEC);
  }
}

Platformio.ini (I also tried the similar option with monitor_filters instead):

monitor_flags =
    --echo
    --eol
    LF
    --filter
    send_on_enter

Under these conditions, I can type whatever, nothing is sent/received.

What I find really weird is that if I use pio device monitor in the terminal, the monitor works almost as I expect:

% pio device monitor -b 9600 --echo --eol LF --filter send_on_enter
--- Available filters and text transformations: colorize, debug, default, direct, hexlify, log2file, nocontrol, printable, send_on_enter, time
--- More details at https://bit.ly/pio-monitor-filters
--- Miniterm on /dev/cu.usbserial-AB0LRFSL 9600,8,N,1 ---
--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---

received:10

received:10
a
received:97
received:10
b
received:98
received:10
c
received:99
received:10

--- exit ---

I say almost because I do have to type Enter twice the first time, which is weird but not a big deal.

Any suggestion on how to ensure in platformio.ini (or some other configuration file) that the serial monitor sends the requested EOL character when using send_on_enter?

[omicronns]

I have same issue. It seems like if --eol is one of LF or CR and combined with --filter send_on_enter it sends nothing, never. It works ok only when --eol is CRLF.