User's Manual

GL865 Hardware User Guide

1vv0300910 Rev.1 – 2011-07-22

page 47 of 79

9.4. 5V UART level translation

If the OEM application uses a microcontroller with a serial port

(UART) that works at a voltage different from 2.8 - 3V, then a

circuitry has to be provided to adapt the different levels of

the two set of signals. As for the RS232 translation there are a

multitude of single chip translators. For example a possible

translator circuit for a 5V TRANSMITTER/RECEIVER can be:

TIP:

Note that the TC7SZ07AE has open drain output; therefore the

resistor R2 is mandatory.

NOTE:

The UART input line TXD (rx_uart) of the GL865 is NOT internally

pulled up with a resistor, so there may be the need to place an

external 47KΩ pull-up resistor, either the DTR (dtr_uart) and

RTS (rts_uart) input lines are not pulled up internally, so an

external pull-up resistor of 47KΩ may be required.