[common error] UART cannot receive data error

utilize FPGA control DAC Experiment of generating waveform

After completing the utilization FPGA control DAC In the experiment of , In the face of UART When sending data , Shows that the interrupt has been turned on , But send the data to the past , No interrupt is displayed , It is equivalent to sending data and knowledge , And not received , after debug after , It turned out to be in the hardware ,vivado Medium BD in ,UART1 Where Bank1 The voltage in is set to 3.3v, After reading the schematic diagram of the development board, I found that it should be set to 1.8v, Set to 3.3v The reason why the data cannot be received is . Pictured , stay UART_RX When receiving in , Because in FPGA The voltage given at one end is 3.3v, Therefore, it can meet 1.8v Voltage requirements , Data can be sent to UART, But in UART Send data to FPGA when , because FPGA The voltage given is marked 3.3v, According to the second figure, we can see , To be in the on state , That is, pull up , The minimum voltage is 2.4v Talent , But to UART1 The voltage provided is only the highest 1.8v, In this way, you will not be satisfied 3.3v Voltage requirements , It will always be in a low state , Data cannot be sent to FPGA End , The returned data cannot appear on the serial port .