User`s guide

USB-UART A
Enabling USB-UART A
communication
page 22
The UART (universal asynchronous receiver/trans-
mitter) is one of the most common ways of exchanging
data between the MCU and peripheral components. It is a serial
protocol with separate transmit and receive lines, and can be used for
full-duplex communication. Both sides must be initialized with the
same baudrate, otherwise the data will not be received correctly.
Modern PC computers, laptops and notebooks are no longer
equipped with RS-232 connectors and UART controllers. They
are nowadays replaced with USB connectors and USB
controllers. Still, certain technology enables UART
communication to be done via USB connection.
Controllers such as FT232RL from FTDI® convert
UART signals to the appropriate USB standard.
USB-UART A communication is being done
through a FT232RL controller, USB connector
(CN7), and microcontroller UART module. To establish
this connection, you must connect RX and TX lines
of the microcontroller to the appropriate input and
output pins of the FT232RL. This selection is done
using DIP switches SW10.1 and SW10.2.
In order to use USB-UART A module on EasyMx PRO
™
v7,
you must rst install FTDI drivers on your computer. Drivers
can be found on Product DVD:
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DVD://download/eng/software/development-tools/
universal/ftdi/vcp_drivers.zip
EasyMx PRO
v7
USB UART A
CONNECTOR
1
2
3
4
5
6
7
8
9
10
11
12
13
14 15
16
17
18
19
20
21
22
23
24
25
26
27
28
TXD
DTR#
RTS#
VCCIO
RXD
RI#
GND
NC
DSR#
DCD#
CTS#
CBUS4
CBUS2
CBUS3
CBUS0
CBUS1
OSCO
OSCI
TEST
AGND
NC
GND
GND
VCC
RESET#
3V3OUT
USBDM
USBDP
FT232RL
U2
FT232RL
VCC-3.3V VCC-5V
C11
100nF
LD7 LD8
RX-LED1
TX-LED1
R12
4K7
R11
2K2
VCC-3.3V VCC-3.3V
R18
4K7
R19
10K
1
2
3
4
VCC
GND
D-
D+
CN7
USB B
C3
100nF
C4
100nF
E1
10uF
VCC-5VVCC-5VVCC-3.3V
FTDI1-D_N
FTDI1-D_P
RX TX
1 2 3 4 5
6
7 8
O
N
SW10
TX-FTDI1
RX-FTDI1
PA1
PA0
DATA BUS
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20122011
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In order to enable USB-UART A
communication, you must push
SW10.1 (PA1) and SW10.2 (PA0)
to ON position. This connects the
RX and TX lines to PA0 and PA1
microcontroller pins and its UART
module.
Figure 8-1:
USB-UART A
connection
schematics