User's Manual

EK-RA4W1 5. User Circuits
R20UT4683EJ0100 Rev.0.90 Page 15 of 30
Apr.28.20
5.4 USB-to-Serial Conversion
USB connector CN5 is connected to the USB-to-serial conversion module from FTDI and can be used as a
virtual COM port. Table 5-2 shows the connection relationship of USB-to-serial signals.
Table 5-2 Names of the USB-to-Serial Signals
Signal Name
Function and Usage
MCU
Port
Pin
TXD
Signal for transmitting data
P205
8
RXD
Signal for receiving data
P206
7
CTS
Input signal for controlling the start of transmission and reception of data
*
1
RTS
Output signal for controlling the start of transmission and reception of data
*
1
Note: This port is not connected on the board as shipped.
The first time the CPU board is connected to the USB port of a PC, the monitor of the PC shows the message
stating that installation of the driver is in progress as shown in Figure 5-3. After that, a message indicating
completion of the driver installation is displayed. The content of the message will differ with the OS version on
the host PC.
Figure 5-3 Displays Indicating Installation of the USB Driver
If you do not have a driver, download the installer for the driver from the Web site of FTDI.
5.5 ACT LED
The ACT LED displays the state of operation of the emulator control software. The illumination conditions are
listed below. The LED is green.
 Illuminated: Indicates that the host machine (PC) has recognized the emulator.
 Not illuminated: Indicates that the emulator cannot be used for some reason (including its power being off).
5.6 Power LED
While the power LED is illuminated, power is being supplied to the board. The LED is green.
5.7 User LEDs
The optional user LEDs can be used for any purpose. LED0 and LED1 are mounted on the board and are
respectively connected to the following ports. The LEDs are green.
 LED0: Pin 21, connected to port P106
 LED1: Pin 46, connected to port P404