User's Manual

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 input lines working at 2.8VCMOS can be pulled-up with 47KΩ
In case of reprogramming of the module has to be considered the use of the RESET line to start
correctly the activity.
The preferable configuration is having an external supply for the buffer.
9.3. UART Behaviour
The UART ports have a different behaviour according to the module’s selected functional mode
(i.e. Power Saving).
Please refer to the SW User Guide to have a full overview of the Serial port signals behaviour in
the different selected conditions.