User manual

LPC4357 Developer’s Kit - User’s Guide

Page 28

4.16 SP9: RS232 Interface

There is a RS232 interface with all modem signals on the board. The RS232 interface is available on a

9-pos male DSUB. The OEM Base Board is a DTE (Data Terminal Equipment). An external device can

be a DCE (Data Communications Equipment). For connecting DTE-to-DCE a straight-thru cable shall

be used. An external device can also be a DTE. For connecting DTE-to-DTE a null-modem cable shall

be used (also called a crossover cable).

See picture below for locating relevant components on the board. The table below lists signal

connections. Note that for the LPC4357 OEM board, which has 32-bit databus, the UART signals

(Rx/Tx and modem signals) are not available at the same place as other OEM boards. The upper half

of the databus occupies the signals used in this interface. Therefore, J18 has to be used to allow

custom connection of the signals needed. The needed signals can be wired from J3, J4 and J5.

Note that it is possible to connect just the RxD/TxD UART signals to the UART multiplexor (USART#3

used) by placing jumpers in position 2-3 in JP12 and JP13. In this case, it will not be a full modem

RS232 interface but RxD/TxD will still be available.

The interface component used (SP3243E) has built-in ESD protection.

Figure 17 – RS232 Interface

Signals

LPC4357

GPIO25_RXD

P2_4 via multiplexor, USART#3 is used

GPIO24_TXD

P9_3 via multiplexor, USART#3 is used

RS232 DSUB-9 Connector

J17

RS232 Modem Connection

JP11 – remove all jumpers!

RS232 Custom Connector

J18

RS232 Modem Connection

Upper: JP12

Lower: JP13

Left pos: 1-2, Right pos: 2-3

Place in pos 2-3, or no

jumpers at all!