User's Manual

GE865 Hardware User Guide
1vv0300799 Rev.11 13-07-2010
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9.3 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 GE865 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.