Override `extra_flags` Generates Warnings

lbussy · March 3, 2023, 12:37pm

Hello,

I am trying to bring a new board into my ecosystem, the Lolin S2-Mini. When I started this of course I thought if it looked like the D1, the port should be easy. Right? Yeah …

Anyway, I use the TelnetSpy library to overload Serial to provide a telnet connection. I get the following error on compile:

.pio/libdeps/lolin_s2_mini/TelnetSpy/TelnetSpy.cpp: In constructor 'TelnetSpy::TelnetSpy()':
.pio/libdeps/lolin_s2_mini/TelnetSpy/TelnetSpy.cpp:43:13: error: cannot convert 'USBCDC*' to 'HardwareSerial*' in assignment
  usedSer = &Serial;
             ^~~~~~

and here is the relevant section:

github.com

yasheena/telnetspy/blob/e1f6c8d0c6ab6bf6f7a98bdf8d56c80e7095507b/TelnetSpy.cpp#L43


      
          

          static void TelnetSpy_ignore_putc(char c) {;

          }

          

          TelnetSpy::TelnetSpy() {

          	port = TELNETSPY_PORT;

          	telnetServer = NULL;

          	started = false;

          	listening = false;

          	firstMainLoop = true;

          	usedSer = &Serial;

          	storeOffline = true;

          	connected = false;

          	callbackConnect = NULL;

          	callbackDisconnect = NULL;

              callbackNvtBRK = NULL;

              callbackNvtIP = (void(*)()) 1;  // 1 => use ESP.restart;

              callbackNvtAO = (void(*)()) 1;  // 1 => use TelnetSpy.disconnectClient()

              callbackNvtAYT = NULL;

              callbackNvtEC = NULL;

              callbackNvtEL = NULL;

I did a little digging and found that the USB CDC is a new-ish implementation. So then I found this:

github.com

platformio/platform-espressif32/blob/8565a828b108b5d9df060b5e60cb3a6e4f65164a/boards/lolin_s2_mini.json#L10


      
          {
            "build": {
              "arduino": {
                "ldscript": "esp32s2_out.ld"
              },
              "core": "esp32",
              "extra_flags": [
                "-DARDUINO_LOLIN_S2_MINI",
                "-DBOARD_HAS_PSRAM",
                "-DARDUINO_USB_CDC_ON_BOOT=1"
              ],
              "f_cpu": "240000000L",
              "f_flash": "80000000L",
              "flash_mode": "dio",
              "hwids": [
                [
                  "0X303A",
                  "0x80C2"
                ]
              ],

I thought to myself, “self, why not disable that?” So I dutifully added those lines to the pio.ini:

build_flags =
    -D ARDUINO_USB_MODE=0
    -D ARDUINO_USB_CDC_ON_BOOT=0

So I can compile, but I get thousands (maybe not thousands, but a lot) of warnings about the redefine:

<command-line>: warning: "ARDUINO_USB_CDC_ON_BOOT" redefined
<command-line>: note: this is the location of the previous definition

I realize just making an error go away may not be the right way to go, so I guess that’s my first question. Am I going about this correctly? If so, is there any way to “undefine” the json settings before I define again? Without creating a new board type of course.

lbussy · March 3, 2023, 6:42pm

Everyone likes answering their own question.

I guess ultimately this boiled down to the differences between Serial on a UART and Serial on USBCDC. A collaborator listened to me complain and something clicked for him, so here are his changes to the library I was working with. Maybe these will help someone: