USART

The EVK1100 provides two USART Interfaces: Usart 0 and Usart 1 RS232 level converters provide proper voltage levels for compliance to the RS232 standard.

Two RS232 connectors are available:



Pinout

These two USART Interfaces are connected through level adapter to two DB9 connectors.These have the following pinout:

GPIO Name Alternate function used
PA 01 U0_TX
PA 04 U0_CTS
PA 00 U0_RX
P4 03 U0_RTS
PA 05 U1_RX
PA 06 U1_TX
PA 08 U1_RTS
PA 09 U1_CTS
PB 23 U1_DCD
PB 24 U1_DSR
PB 25 U1_DTR
PB 26 U1_RI

Hardware Schematic

Figure 1. USART0 Connection

Figure 2. USART1 Connection

Modem connection

With the fix explained just below, the cable to use to connect the EVK1100 USART 1 to any DCE is a male-male crossover DB9 cable with 9 conductors including shield, or any equivalent configuration:

     MODEM|                          |EVK1100 USART1
       DCE|                          |DTE
     DB9-F|DB9-M                DB9-M|DB9-F
          |                          |
          |                          |
FGND Shield-Shield ----------  Shield-Shield FGND 
          |                          |
          |                          |
DCD      1-1 ---------------------> 1-1      DCD
          |                          |
          |                          |            
 TX      2-2 <---------  ---------> 2-2      TX
          |            \/            |
          |            /\            |
 RX      3-3 ----------  ---------- 3-3      RX
          |                          |
          |                          |
DTR      4-4 <-------      -------> 4-4      DSR
          |          \    /          |
          |           \  /           |
GND      5-5  ---------\/---------  5-5      GND
          |            /\            |
          |           /  \           |
DSR      6-6 ---------    --------- 6-6      DTR
          |                          |
          |                          |
CTS      7-7 <---------  ---------> 7-7      CTS
          |            \/            |
          |            /\            |
RTS      8-8 ----------  ---------- 8-8      RTS
          |                          |
          |                          |
 RI      9-9 > ------------------ > 9-9      RI