User's Manual

Page 19 of 31
2.2.8.2 Reference circuit
The reference circuit of UART interface is shown in Figure 2-11.
1) As the UART interface can only supply TTL level while the PC serial port is RS232 level, it requires to use level
conversion device. The reference device is SP3238EEA which provided by SIPEX, as shown in Figure 2-11. J401 is
a 9 pin serial port socket which can connect to PC with serial cable.
2) To avoid static electricity, it is recommended to use the ESD protection device for the signal line of the UART socket.
Just like the varistors RV401, RV402, RV403, RV404 and RV405 in Figure 2-11 which should be close to the
socket as possible.
Figure 2-11 The reference circuit of UART interface
2.2.9 LED control
2.2.9.1 Description
There are two pins for LED control by the 60 PINs board to board connector. The detail information is given in Table
Rx UART_RX 56 Rx in UART
Tx UART_TX 54 Tx in UART
GND GND
7, 8, 13, 14, 16, 19, 22, 26,
27, 30, 36, 40, 42, 47, 55, 59
GND