std::cin should be implemented in terms of linenoise (IDFGH-8199)

[frak0d]

Is your feature request related to a problem?

std::cin doesn't work. it doesn't read anything from serial console. everyone says "use linenoise", but why not just implement std::cin using linenoise ? if std::cout works over serial, then std::cin should also work over serial.

Describe the solution you'd like.

std::cin should be implemented in terms of linenoise.

Describe alternatives you've considered.

No response

Additional context.

No response

[igrr]

Hi @0xb00b,
By default, ESP-IDF sets up the standard I/O streams (stdin, stdout, stderr) to use the simple non-interrupt-driven UART driver (docs. This driver provides a blocking stdout and non-blocking stdin. Most C standard library functions (as well as C++ functions built on top of them) expect stdin to be blocking. This is why functions such as scanf (and the equivalent C++ functions) don't behave as expected by default.

Applications which require a blocking stdin behavior need to set up the interrupt-driven UART driver (uart_driver_install) and reconfigure the console streams to work with that driver (esp_vfs_dev_uart_use_driver). The code snippet for doing this can be found here.

While I agree that it's annoying that std::cin doesn't work "out of the box", it is unlikely that we will be modifying the standard library to perform such initialization automatically.

[frak0d]

@igrr thanks, that almost works. I can't see my input while typing in serial console, but otherwise it works.

I suggest adding this information from your comment, to documentation as a highlighted note for others like me.

[finger563]

@0xb00b did you figure out how to get the input to show when typing (when using std::cin / std::getline / etc.)?

[frak0d]

@0xb00b did you figure out how to get the input to show when typing (when using std::cin / std::getline / etc.)?

No, i didn't bother with it.

Perhaps you can print out characters manually as you recieve them one at a time. There must be some low level function to read serial input in realtime without needing to press enter key.

[finger563]

Yea I ended up using

        char c;
        while (in.get(c)) {
          line += c;
          cli::Cli::cout() << c;
          if (c == '\n')
            break;
        }

instead of the simpler std::getline(in, line) interface, but it doesn't handle backspace and such well :/

[joaotavora]

After using the linked code, local echo works fine as long as the dev is configured properly and a simple client such as socat is used:

❯ stty -F /dev/ttyUSB0
speed 115200 baud; line = 0;
min = 0; time = 0;
-brkint -icrnl -imaxbel
-opost -onlcr
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke

I think the "echo" properties there are important. The loop I'm using is straightforward and does use std::getline(in, line)

  std::string s;

  std::cout << "Prompt: ";
  while (std::getline(std::cin, s)) {
    std::cout << "Read: '" << s << "'\nPrompt:";
  }
  std::cout << "Bye bye!" << s;

With pyserial's miniterm you can also set local echo. The screenshot is from socat though. Haven't figured out what to send to break the loop cleanly yet.

[Bobobel]

I am having the same problem with unblocking stdin but with preferable 'usb-serial-jtag' (and ESP-BOX-3). I have tried the example init from "esp_zigbee_gateway.c", but without any blocking.
I would very much appreciate some additions to the documentation!

IGRR code snippet from </examples/common_components/protocol_examples_common/stdin_out.c> together with "CONFIG_ESP_CONSOLE_UART_DEFAULT=y" failed with:
"Writing to serial is timing out. Please make sure that your application supports an interactive console and that you have picked the correct console for serial communication."
Maybe "esp_vfs_dev_uart_register();" is missing? I had a try: No!
I am realy frustrated: with BOX-3 almost any example shows severe errors! HELP!

[igrr]

@Bobobel if you are using usb_serial_jtag interface, my suggestion doesn't apply literally, as it was written for the UART interface. Instead, you need to select the USB_SERIAL_JTAG as the primary console output in menuconfig, initialize the usb_serial_jtag driver and then call esp_vfs_usb_serial_jtag_use_driver.

[Bobobel]

Dear Ivan,
thank you very much. As always, you feel responcible and answer quickly. I am very happy again >:->
I tried all that: set jtag in menuconfig and initialize the usb_serial_jtag driver and then call esp_vfs_usb_serial_jtag_use_driver.
setting uart in menuconfig and doing the uart setup as explained above in issues/9692. For output I had to add the 'esp_vfs_dev_uart_register();'.
For jtag I used a second uart and esp_vfs_dev_uart_register(); for output, otherwise I did not see any output. Funny effect: Now I see a write timeout dispite the setup of no watchdog at all (as far as I do understand and see) in menuconfig.
No I am trying 'esp consol system', but that overkill for my opinion.

[igrr]

For jtag I used a second uart and esp_vfs_dev_uart_register();

I'm sorry, I'm failing to understand what you are trying to achieve. Please open a new issue and describe the original problem you want to solve, as well as mention the IDF version you are using.