Previously on “Practical Testing”… To deal with some specific usage scenarios of a piece of general purpose code I’m in the process of implementing a timer wheel that matches the interface to the timer queue that I previously developed in this series of articles. Last time I left myself with a failing test. The problem is that setting a new timer on the timer wheel sets a timer that’s relative to the time that timer wheel thinks is ’now’ and the timer wheel’s view of the current time could be slightly behind reality; see the previous entry for a diagram that explains the problem.
Previously on “Practical Testing”… To deal with some specific usage scenarios of a piece of general purpose code I’m in the process of implementing a timer wheel that matches the interface to the timer queue that I previously developed in this series of articles. The timer wheel trades space for speed and so far the development has gone well as I’ve been able to use the tests that I had already developed for the previous implementations to guide the new development.
I’m in the process of implementing a timer wheel that matches the interface to the timer queue that I previously developed in this series of articles. The idea being that for certain specific usage scenarios the timer wheel will perform better than the timer queues. Last time I refactored the tests that I was using for the timer queues to remove duplication and I now have a set of failing tests for the new timer wheel.
The most recent articles in the “Practical Testing” series have been discussing the performance of the timer queue that we have built. As I hinted when I first brought up the performance issues, the particular use case that I have which is causing problems might well be more efficiently dealt with using a different (more specialised and less general purpose) design.
The timer queue has adequate performance for general purpose use and can handle timers set within a range of 0ms to 49.
The previous article in the “Practical Testing” series set things up so that we can measure the performance of the code under test with the intention of trying to improve performance for a specific set of use case scenarios. This time around I’ll make a few changes which I hope will improve the performance and measure the effects of the changes with the performance tests that I added last time.
Back in 2004, I wrote a series of articles called “Practical Testing” where I took a piece of complicated multi-threaded code and wrote tests for it. I then rebuild the code from scratch in a test driven development style to show how writing your tests before your code changes how you design your code. Since the original articles there have been several bug fixes and redesigns all of which have been supported by the original unit tests and many of which have led to the development of more tests.
Previously published This article was previously published on lhexapod.com as part of my journey of discovery into robotics and embedded assembly programming. A full index of these articles can be found here.
This is the AVR Studio project and assembly language source code files for the latest version (v7.0) of my 64 channel serial servo controller.
This is the latest version of the ATMega168 version of the code which includes all of the new servo commands that I wrote about here including the multi-move command and the unit tests that I spoke of here.
Previously published This article was previously published on lhexapod.com as part of my journey of discovery into robotics and embedded assembly programming. A full index of these articles can be found here.
This is the source code for the latest version of the 64 channel servo controller as detailed here.
This is an ATMega168 version of the controller that was originally developed for the ATtiny2313 but which was ported to the ATMega when I ran out of memory on the ATtiny.
Previously published This article was previously published on lhexapod.com as part of my journey of discovery into robotics and embedded assembly programming. A full index of these articles can be found here.
The 64 channel serial servo controller that I’ve been developing works pretty well for me but most of my development and testing was done in the AVR studio simulator. Once I actually started working with my hardware again I noticed a slight problem.
Previously published This article was previously published on lhexapod.com as part of my journey of discovery into robotics and embedded assembly programming. A full index of these articles can be found here.
The time has finally come to put all of the code from the last three parts of this article together to form a complete serial configured, 64 channel, PWM servo controller for the ATTiny2313 and several CD74HCT238Es.
