Stm32f407ve ADC+DMA used 1KHz sin is not read evenly when reading the reason

[Jkong.1]

Stm32f407ve used ADC+DMA used 1KHz sin is not read evenly when reading the reason

External 8MHz crystal and UART asynchronous use

[Tesla DeLorean]

You don't look to be pacing with a TIM, assume that you are saturating the USART.​

[Jkong.1]

I did not use the TIM. How to fix if USART is saturated? The code using USART was uploaded as a photo attachment.