Chameleon-PIC Nurve Networks, Chameleon-PIC Datasheet - Page 35

• Manufacturer Part Number: Chameleon-PIC
• Description: MCU, MPU & DSP Development Tools PIC24 & PROPELLER DEV SYSTEM (SBC)
• Manufacturer: Nurve Networks

Specifications of Chameleon-PIC

• Processor To Be Evaluated: PIC24
• Data Bus Width: 16 bit
• Interface Type: USB, VGA, PS/2, I2C, ISP, SPI
• Operating Supply Voltage: 3.3 V, 5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

© 2009 NURVE NETWORKS LLC “Exploring the Chameleon PIC 16-Bit”
6.0 USB Serial UART
Figure 6.1 – The FTDI USB to Serial UART.
Referring to Figure 6.1, this is the USB to serial converter designed into the Chameleon PIC. It’s based on a FTDI
FT232R USB to serial UART chip. The chip works by converting a USB packet stream into a standard serial port signal
set. Of course, the other end of the USB cable has to be plugged in a PC running the custom FTDI USB drivers that
create “virtual” COM ports from the operating system’s perspective. This magical little chip lets us talk serial to the
Chameleon with a USB port. FTDI has written drivers for Windows, Linux, and Mac OS X, so these chips are quite
popular since it’s very difficult to find a real DB9 RS-232 serial port on a PC anymore. You can take a look at the data
sheet for the chip here:
DVD-ROM: \ CHAM_PIC \ DOCS \ DATASHEETS \ DS_FT232R.pdf
Considering all that, let’s take a quick look at the design. The USB cable from the PC plugs into H1 (which is a Mini-B
USB header) the USB packets are converted into a serial stream by the chip and the standard RS-232 signals are
generated by the chip. We are only interested in TX/RX and DTR (data terminal ready) which is used to reset the
Propeller and PIC by both the Propeller tool and bootloader tools respectively. The TX/RX signals are routed to both the
Propeller and PIC chips where they are interfaced to the appropriate I/O pins. Additionally, at the top of the schematic you
see the signal USB_5VOUT, this is the power coming in from the USB port header, this is routed to the system as 5V
power when there is no external 9V supply plugged in. However, if you are going to use the Chameleon without a 9V
power supply and power it from the USB port, I highly recommend you use a powered USB hub since the Chameleon will
draw up to 200mA or more as it throttles its performance and powers up all its peripherals.
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