ReadFile() gives error 998 when trying to read data from USB port

Question

I'm trying to send data from a STM32 Discovery Board to a host PC via USB using my own application. I managed to send data to the STM. I used WriteFile for that. For reading data I am calling the function readSerialPort() which calls the function ReadFile().

In main.c readSerialPort() is called in the while loop. Whenever I send some testdata (4 random bytes) to the PC I can see status.cbInQue get bigger with 4, but ReadFile does not return TRUE, as to show it has finished putting the data in the buffer pointer leading to receivedData().

When I do GetLastErrror(), it returns error code 998. Which means ERROR_NOACCESS, usually this means that the allocated array is not the same as buf_size, but it is. So what causes this error and makes receiving data from the STM via USB not possible?

(I'm pretty new to asking a question on Stackoverflow so let me know if I need to improve in the way I'm asking this question)

main.c

char* receivedData[31];     
uint32_t id = 0;        
while(1) {  
if (readSerialPort(*receivedData, 31)) {
    printf("%d - %s\n", id, receivedData);
    id++;       
} else {            
    printf("error %u\n", GetLastError());       
}

comm.c

#include "comm.h"

HANDLE handler;
uint8_t connected;

COMSTAT status;
DWORD errors;

int connectSerial(char* portName) {
    connected = 0;
    handler = CreateFileA(portName,
                                GENERIC_READ | GENERIC_WRITE,
                                0,
                                0,
                                OPEN_EXISTING,
                                FILE_ATTRIBUTE_NORMAL,
                                0);
    if (handler == INVALID_HANDLE_VALUE) {
        if (GetLastError() == ERROR_FILE_NOT_FOUND) {
            printf("ERROR: Handle was not attached. Reason: %s not available\n", portName);
        } else {
            printf("ERROR!!!");
        }
    } else {
        DCB dcbSerialParameters = { 0 };

        if (!GetCommState(handler, &dcbSerialParameters)) {
            printf("failed to get current serial parameters");
        } else {
            connected = 1;
            PurgeComm(handler, PURGE_RXCLEAR | PURGE_TXCLEAR);
            //  Sleep(2000);
        }
    }
}

void disconnectSerial() {
    if (connected) {
        connected = 0;
        CloseHandle(handler);
    }
}

uint8_t readSerialPort(char* buffer, unsigned int buf_size) {
    DWORD bytesRead;
    unsigned int toRead;

    ClearCommError(handler, &errors, &status);

    if (status.cbInQue > 0) {
        if (status.cbInQue > buf_size) 
            toRead = buf_size;
        else
            toRead = status.cbInQue;
    }

    if (ReadFile(handler, buffer, toRead, &bytesRead, NULL))
        return bytesRead;
    return 0;
}

uint8_t writeSerialPort(char* buffer, unsigned int buf_size) {
    DWORD bytesSend;

    if (!WriteFile(handler, (void*)buffer, buf_size, &bytesSend, 0)) {
        ClearCommError(handler, &errors, &status);
        return 0;
    }
    else return 1;
}

Answer 1

Johnny's first comment solved my problem:

char* receivedData[31]; is an array of uninitialized pointers. Did you mean char receivedData[31];? And then call: if (readSerialPort(receivedData, 31)) {