STM32 Timer (pwm) vs usart

[Feco]

Hello.
I wanted to make a led design with controllable brightness. The controlling would work via usart ('0' = darkest --- '9' = brightest, simple) It works good, BUT it doesn't receive every command. If I press a button, sometimes it takes 4-5 presses to receive the data, no idea why. Could you please point out what I did wrong in my code?

include <stm32f10x.h>

int indata;

int usart_rec(void) {
    while(!(USART1->SR &= USART_SR_RXNE));
    return USART1->DR & 0x1FF;
}

void usart_snd(int data) {
    while(!(USART1->SR & USART_SR_TXE));
    USART1->DR = data;
}

int main(void) {
    RCC->APB2ENR |= RCC_APB2ENR_IOPCEN | RCC_APB2ENR_IOPAEN | RCC_APB2ENR_USART1EN | RCC_APB2ENR_AFIOEN;
    RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;
    AFIO->MAPR = AFIO_MAPR_TIM3_REMAP;
    GPIOA->CRH = GPIO_CRH_CNF10_0 | GPIO_CRH_CNF9_1 | GPIO_CRH_MODE9_0;
    GPIOC->CRH = GPIO_CRH_CNF8_1 | GPIO_CRH_MODE8_0;

    USART1->BRR = SystemCoreClock/115200;
    USART1->CR1 = USART_CR1_RE | USART_CR1_TE | USART_CR1_UE;

    TIM3->PSC = 239;
    TIM3->ARR = 1000;
    TIM3->CCR3 = 0;
    TIM3->CCMR2 = TIM_CCMR2_OC3M_2 | TIM_CCMR2_OC3M_1;
    TIM3->CCER = TIM_CCER_CC3E;
    TIM3->CR1 = TIM_CR1_CEN;

    while(1) {
        indata = usart_rec();
        TIM3->CCR3 = ((indata-48)*100);
        usart_snd(indata);

    }
}

Thanks.