Arduino for STM32

well, I'm not too sure about your codes, but that Serial (including USB serial and HardwareSerial) uses a ringbuffer.
If the receiving end did not read the buffer, it is possible that it gets filled.
I reviewed the codes and found that there is
Serial.availableForWrite()

virtual int ...

well, format your post, comment so that it is more readable, e.g.

for (uint16_t A = 0; A < 15; A++) {
Serial.println(A);
filterxo[A] = getdouble();
Serial.println(filterxo[A], 3);
Serial.read(); // get rid of spacer/term char x
}


did you declare your filterxo array properly? e.g.

#include ...

As a bit different test, this shows a USB buffer size of 64 bytes max, but prints about 128 before losing it. The string variable teststr can go long if hardcoded:

else if (cmmd == 'c') {
while (Serial.available() == 0) {}
Serial.print("string started ");
Serial.println(Serial.available ...

I started (as a non programmer) with Thomas Roell and the Ladybug board. I used his board files and library forever.
Now Im porting to the STM32duino Core. Got through most porting issues with Generic L432KCUx series setting. But I used to write from a PC to my board through USB a large chunk of ...

Hi everyone: i received in these days a custom PCB i designed based on the STM32F411 microcontroller:

I wanted to experiment with such MCUs and make a custom board with them for the first time; i was also interested in making it compatible with the arduino framework through PlatformIO as i already ...

First a big ' Thank You! ' to the maintainers of this toolset and forum. I was able to rediscover and find new uses for my outdated and unsupported Netduino 2 board. A board I thought was obsolete. I'm still exploring how I can use STM32duino with this board but getting it programmed via the Arduino ...

I reviewed the codes, and it is quite 'convoluted'
when HardwareSerial initializes
https://github.com/stm32duino/Arduino_Core_STM32/blob/main/cores/arduino/HardwareSerial.cpp#L133
it configures the pins according to PeripheralPins.c
https://github.com/stm32duino/Arduino_Core_STM32/blob/main ...

I understand now, thank you! Yes, I have CDC supersede. I looked in WSerial.h to understand a bit more and it looks like that's done by this block

#if defined (USBCON) && defined(USBD_USE_CDC)
#ifndef DISABLE_GENERIC_SERIALUSB
#define ENABLE_SERIALUSB
#if !defined(Serial)
#define Serial ...

from the arduino menu, if you select "USB Support - CDC (generic 'Serial' supersede U(S)ART"
USB-Serial become the definiition of Serial

hence when you issue

void setup() {
Serial.begin();
}

that goes to USB-Serial. Serial1 .. Serial4 are still there but those are HardwareSerial which goes to ...

Thanks for the replies. Could you please explain more what you mean by override with USB serial? Serial over USB is working fine but do you think it could be causing my issue?

Here's what I have for my clock configuration. I took this from the firmware that comes with the board.

void SystemClock ...