CYUSB3KIT-001 EZ-USB FX3 Development Kit Guide, Doc. #: 001-70237 Rev. *C
19
Getting Started
Most FX3 GPIO pins can be programmed to attach an internal pull-up or pull-down resistor to
prevent floating inputs. This example uses two GPIO pins that are programmed as a group to serve
as UART signals. Because the serial debugger does not use the UART CTS and RTS signals, these
pins can be used for the LED and push button. There is no need for an external pull-up resistor on
the GPIO[53] (UART RTS) signal since an internal pull-up resistor is enabled in the FX3 firmware.
Two jumpers need to be in place to connect the GPIO[53] and GPIO[54] signals to the J34 header:
Jumpers J101 and J102 should short pins 2–3 (green rectangle in
Figure 2-15
). Adjacent jumpers
J103 and J104 should short pins 1–2 to connect the RXD and TXD UART signals to the DB-9
connector. Jumper J53, just above the power switch (yellow rectangle) must also be in place to
enable USB power to the board.
Table 3-1 on page 35
gives all the FX3 jumper settings and their
purposes.
Figure 2-15. FX3 SDK board with Added Circuit on J34, Jumpers, Power Switch
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