Neoway N21 Series Hardware User's Manual

Neoway N21 Series Hardware User's Manual Manual pdf 24 page image

N21Hardware User GuideCopyright © Neoway Technology Co., Ltd. All rights reserved. 15In all reference designs of this section, the signals of pins on the module is named in perspective ofmodule while peripheral pins are named from the view of the components. For example, UART_TXDindicates the pin that the module sends data while MCU_RXD indicates the pin that MCU receives data.These two pins should be connected.Please note the signal naming of pins on the components in peripheral selection and design.3.3.1 UARTSignal Pin I/O Function RemarksUART_TXD 14 DO Data transmittingUART_RXD 13 DI Data receivingN21 provides one UART interface that supports automatic baud rate detection. The level at the UARTinterface is 2.8V.Figure 3-11 UART connectionUART_RXDUART_TXDMCU_TXDMCU_RXDGND GNDN21module ClientSchematic Design Guidelines Note the match of signals. If the UART does not match the logic voltage of the MCU, add an external level shifting circuit.Three types of level shifting circuit are recommended based on the logic level quality. The first one ispreferred and the other two are cost-effective simple circuits. Note their application senarios.Level shift chip is recommended if the level of MCU is higher than 3.3V or the baudrate is higher than1 MHz. Figure 3-12 shows the reference design.