My ‘TCP/IP Lean’ books are out of print, but I’m still using the same philosophy when designing embedded systems: trying to understand the fundamentals, so as to avoid the bloat that results from a simplistic building-block approach to hardware & software.
So I’m posting some projects taken from my experience working for the Iosoft consultancy, in the hope they will be of use – feel free to adapt and extend them for your own purposes, but please credit this blog as the origin of the material.
Viewing ARM CPU activity in real time
I’ve created a short video of my ‘reporta’ project, demonstrating a real-time graphical display of I/O port activity. The code is pure Python; it accesses the CPU internals via the SWD interface, so its operation is completely transparent to the target CPU.
If you’re not a fan of FTDI hardware, or need a faster debug system, take a look at my post OpenOCD on the Raspberry Pi.
Programming FTDI devices in Python
FTDI chips are frequently used as USB-to-serial adaptors, but the newer devices have the ability to drive more complex protocols such as SPI and I2C.
I like to use Python when first experimenting with new PC hardware, and there are some Python libraries for interfacing to FTDI chips, but I couldn’t find any real projects or complete worked examples.
The following posts demonstrate a step-by-step approach to driving the FTDI chips from Python, to learn about their functionality. In the final part, I implement a pure-Python SWD interface that can access the internals of a CPU while it is running, in a similar way to much more sophisticated debug tools, such as OpenOCD.
Part 1: Initial experimentation
Part 2: Using Linux
Part 3: Using MPSSE to drive an SPI device
Part 4: First steps towards accessing an ARM CPU using SWD
Part 5: Reading CPU internals with SWD
Copyright (c) Jeremy P Bentham 2018. Please credit this blog if you use the information or software in it.