The 7th entry of the Cortex-M3 exception vector is reserved for the 2's complement of the checksum of the exception vector. At run time the bootloader computes the checksum again and adds it to the one stored in the exception vector, if the result equals zero it starts executing the user code.
The checksum is usually computed by the software that flashes the binary like FashMagic or openocd, if you're using openocd like me,...
Monday, October 24, 2011
Tuesday, July 12, 2011
Delay Slots
Delay slots are an artifact of some early pipelined architectures in which pipeline hazards were not handled explicitly. I was puzzled for while by some unexpected assembly produced by gcc while working on my own implementation of the MIPS ISA, further investigation yielded the following results about the branch delay and the load delay slots, both of them occurred in early MIPS architectures.
Load Delay...
Saturday, April 30, 2011
Pimp My Hexbug!
What is a Hexbug you ask ? Well, a Hexbug is a line of micro robotic creatures! Sounds fancy doesn't it ? actually it's quite boring, if you ask me, for example, mine just walks around until it hits something and then it turns around and that's basically just about it! That's why I've decided to reuse the mechanical parts and boost the bug a bit. So I designed a small wireless board to control my Hexbug. This is the modified...
MCP9800 Temperature Sensor
A while ago I picked up a few temperature sensors from DigiKey, it's been in my junk box for sometime now, so I decided it's about time to do something with it!
Features
The MCP9800 is a high accuracy digital temperature sensor from Microchip, the sensor has an I2C interface, a configurable 9-bit to 12-bit temperature resolution, shutdown mode, one-shot mode (one conversion while in shutdown) and finally an interrupt...
Wednesday, March 30, 2011
TCM8230MD Breakout
TCM8230MD
The TCM8230MD is a tiny camera from Toshiba theoretically capable of outputting 640x480@30FPS! This post is to document my experience with this devilish cam.
Breakout
This is my second breakout board for the camera, this one is designed to be connected as a module to another board and doesn't use a crystal oscillator for the clock, I'm using one of the PWM channels instead. However, the older breakout is still...
Tuesday, March 29, 2011
Binary Counters
Binary counters can be used for a variety of things from time keeping to generating/measuring frequencies. Today, we will talk about the concepts behind binary counters using an atmega328 for practice.
Logic!
Let's start with a simple 4-bit counter based on JK flip-flops. A JK flip-flop has the following truth table:
J K Qt+1 State
0 0 Qt No change
0 1 0 Clear
1 0 1 Set
1 1 Qt` Complement
Where Qt is the current...
Saturday, January 1, 2011
Introduction to ARM Cortex-M3 Part 2-Programming
Welcome to the second part of the Introduction to ARM Cortex-M3, in part 1 we went through the core features of the Cortex-M3 and the LPC1768. In this part we will focus more on programming the LPC1768 by covering the following points:
Toolchain overview
Library Tweaks
Hardware Interfaces
Software Stacks
we have a lot to cover so let's get started...
Toolchain overview
The toolchain of choice is the CodeSourcery toolchain,...
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