Cypress CY3640 USB Starter Kit
User’s Guide
Cypress Semiconductor Ver 0.993
Page 11
The cathode of this LED is also connected to a pin on the 40-pin connector (pin 8) and to an
adjacent hole that may be used to install a wire wrap pin. This allows the user to remove the
factory-installed jumper to Vss and use the LED for their own purposes.
Note:
Although it may be convenient to know when the USB is applying power, during
development. The fact that JP1 is left connected to Vss makes the device not strictly
compatible with the USB specification, because it will draw approximately 20 mA whenever it
is connected. The USB specification limits power prior to the device being configured to 500
µA.
The Enumeration LED
The Enumeration LED (as shipped from Cypress) is used to indicate that the USB
Thermometer device has been enumerated. The cathode of the LED is connected to P13
through a jumper (JP2) which controls its path to Vss.
The cathode of this LED is also connected to a pin on the 40-pin connector (pin 10) and to an
adjacent hole that may be used to install a wire wrap pin. This allows the user to remove the
jumper to P13 and use the LED for their own purposes.
The switch (SW1)
SW1 (as shipped) on the Cypress USB Thermometer is used to select whether the
Thermometer Windows application displays the temperature in Centigrade or Fahrenheit. It is
a momentary SPST.
One pole of the switch is connected to Vss. The other pole is connected to Vcc (Vbus)
through R4, to a pin on the 40-pin connector (pin 6), to an adjacent hole that may be used for
installing a wire wrap pin, as well as to the GPIO P12 of the USB controller through a jumper
JP3. This allows the user to remove the jumper to P12 and use SW1 for their own purposes.
The breadboard area
Sea of holes
Cypress has provided an area that will accept wire wrap pins and wire wrap sockets for
development of logic and functionality on the board.
USB Vbus (Vcc) and Vss connections
We have provided locations for connecting power and ground from the USB to your bread
board area. These locations will accept wire wrap pins.
External Vcc connections
If you need to power your breadboard with an external supply, a connector site (P1) is
supplied for that purpose. Two capacitor locations are also provided adjacent to the
connector for bypass. C6 is a bulk bypass and C7 is for high frequency. These capacitors are
not populated with the CY3640 as shipped, and you should use components appropriate to
your needs.
The External Vcc supply is brought to the bread board area and connected to three locations
labeled (oddly enough) Ext. Vcc. You may insert wire wrap pins in these locations to route to
your breadboard area.
The temperature sensor (U2)
The temperature sensor device is socketed so it can be removed if you need to use the
associated pins on the Cypress USB Controller for other logic on your breadboard.
Ferrite bead locations
If noise is a problem in your environment, locations for two ferrite beads (FB1 and FB2) have
been provided: one for the Vcc supply from the USB and one for the Ground return to the
