User's Manual

GE864- QUAD Har dwar e User Guide
1vv0300872 Rev.1 2010-04-02
- All Rights Reserved. Page 44 of 77
9.3. 5V UART Level Translation
If the OEM application uses a microcontroller with a ser ial port (UART) that wor ks at
a voltage different fr om 2.8 – 3V, then a circuitr y has to be provided to adapt the
different levels of the two sets of signals. As for the RS232 translation ther e are a
multitude of single chip translators. For example a possible translator cir cuit for a 5V
TRANSMITTER/RECEIVER can be:
TIP:
This logic IC for the level translator and 2.8V pull- ups (not the 5V one) can be
powered dir ectly from VAUX line of the GE864-QUAD. Note that the TC7SZ07AE has
open dr ain output; therefor e the resistor R2 is mandatory.
TIP:
The UART input line TXD (rx_uart) of the GE864-QUAD 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.