Chameleon-AVR Nurve Networks, Chameleon-AVR Datasheet - Page 131

• Manufacturer Part Number: Chameleon-AVR
• Description: MCU, MPU & DSP Development Tools AVR8 & PROPELLER DEV SYSTEM (SBC)
• Manufacturer: Nurve Networks

Specifications of Chameleon-AVR

• Processor To Be Evaluated: AVR 328P
• Data Bus Width: 8 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 AVR 8-Bit”
As you can see the code to extract and rebuild the SPI packets is tricky, a lot of bit fiddling and masking to get the data
back from the ASM SPI driver that is passing the data into the global shared memory. All packets are 3-bytes long and
look like this:
Command Packet Format
[command8, data_low8, data_high8]
Commands that only require 8-bits of data or operand only use the first data byte, commands that require 2-bytes use
both the low and high. The bottom line is all commands only are 3-bytes, so you can’t send a string or something large,
you have to design your commands so they are simple and can be constructed with only 2 bytes of data at most. Thus,
most commands are atomic in nature. For example, there is no “print string” command, there is only a “print character”
command, but by stringing a collection of “print chars” together at the master/client side you can print a string. All the
commands are designed with this in mind.
16.2 Selecting the Drivers for the Virtual Peripherals
The drivers for each of the media devices were selected based on functionality and popularity. There are definitely better
drivers for many of the devices. For example, more robust graphics drivers, or more advanced sound drivers, etc.
However, this default driver isn’t about using the best, but more about system integration. Thus, drivers that are easy to
interface to and easy to control with a simply subset of commands where used. In the sections below we will cover the
exact drivers used, but the point is, they were chosen more or less for ease of use and user base.
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