Digilent 410-269P-KIT - Manual (Page 3)

chipKIT Cmod™ Reference Manual
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
Page 3 of 11
2 ChipKIT Cmod Hardware Description
MPIDE and USB Serial Communications
The chipKIT Cmod board is designed to be used with the Multi-Platform IDE (MPIDE). The MPIDE development
platform was created by modifying the Arduino™ IDE. It is backwards-compatible with the Arduino IDE.
The MPIDE uses a serial communications port to communicate with a boot loader running on the chipKIT Cmod
board. The serial port on the board is implemented using an FTDI FT232R USB serial converter. Before attempting
to use the MPIDE to communicate with the board, the appropriate USB device driver must be installed.
The chipKIT Cmod uses a standard micro-USB connector for connection to a USB port on the PC. A USB-A to Micro-
B cable, not supplied, is used to connect the board to a USB port on the host computer.
When the MPIDE needs to communicate with the chipKit Cmod board, the board is reset and starts running the
boot loader. The MPIDE then establishes communications with the boot loader and downloads the program to the
board.
When the MPIDE opens the serial communications connection on the PC, the DTR pin on the FT232R chip is driven
low. This pin is coupled through a capacitor to the MCLR pin on the PIC32 microcontroller. Driving the MCLR line
low resets the microcontroller, restarting execution with the boot loader. See the net labeled P32_RST in the
schematic for further detail about this connection. The P32_RST net is also brought out to DIP pin 9.
Two red LEDs (LD1 and LD2) will blink when data is being sent or received between the chipKIT Cmod and the PC
over the serial connection.
Power Supply
The chipKIT Cmod is designed to be powered via USB (J3) or from an external power supply connected to pin 1 of
the DIP package.
The chipKIT Cmod has a single voltage regulator which regulates either 5V from USB, or a maximum of 15V
external voltage. A series diode between the DIP pin 1 (VIN) and DIP pin 3 (USB5V0) prevents an external voltage
applied to pin 1 being fed back onto the USB 5V supply when powering the board via DIP pin 1. All power supply
options are regulated to 3.3 V to provide power to the VCC3V3 bus that powers the PIC32 microcontroller. The
output of the on-board 3.3V regulator is available at DIP pin 2 and can be used to power external circuitry.
The 3.3V regulator is a Microchip MCP1703. The regulator is rated for a maximum output current of 250mA. The
absolute maximum input voltage for the MCP1703 is 16V. This regulator has internal short circuit protection and
thermal protection. It will get noticeably warm when the current consumed by the VCC3V3 bus is close to the
250mA maximum.
5V Compatibility
The PIC32 microcontroller operates at 3.3V. There are two issues to consider when dealing with 5V compatibility
for 3.3V logic. The first is protection of 3.3V inputs from damage caused by 5V signals. The second is whether the
3.3V output is high enough to be recognized as a logic high value by a 5V input. When driving a high impedance
input (typical of CMOS logic), the output high voltage from the PIC32 microcontroller will be close to 3.3V. Some