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.
In my opinion there’s a fundamental design flaw in the both the 8 channel and the 64 channel servo controller firmware that I’ve presented. Both allow the serial data handling code to take priority over the PWM generation code.
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.
Here’s the source code to the 64 channel ATtiny2313 servo controller. Note that you’ll need to use up to 8 CD74HCT238E, or equivalent, demultiplexer chips and that you can adjust the number of servos that you can control in steps of 8 using as many or as few CD74HCT238E chips as you want.
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.
I’ve been experimenting with the servo controller that I developed for the ATtiny2313 here and the demultiplexing chips that I mentioned here. The result is a 64 channel servo controller that seems to work pretty well. Right now I haven’t breadboarded all 64 channels, I have two of the CD74HCT238E chips connected to the ATtiny but I/O pins and he firmware would drive 8 of them if they were connected to give 64 channels.
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 jitters and general instability of the hacked together simple servo controller (see here) for the ATtiny2313 were, it seems, down to the fact that the internal clock wasn’t stable enough and this caused enough timing issues to throw the PWM off enough to jiggle the servo position around rather than hold it steady.
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.
My progress has been slow over the past couple of weeks because a) I’ve been rather busy with other things and b) an order of components has gone missing in the post. The order contains some 4mhz crystals and therefore my server controller firmware testing has been on hold as I’d like to remove the potential clock instability as a potential cause of the controller jitters before continuing my debugging.
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 morning I tested the first version of my custom servo controller. It’s currently heavily based on the source for 16 channel servo controller that I’ve mentioned before. What I did was simply adjust that source for my target processor and the fact that I’m using it with a 4Mhz internal clock rather than the more standard “RS232 baud rate friendly” 3.
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.
I’ve been spending some time getting to know AVR Studio 4, especially the simulation and debugging functionality. It’s a very functional and very useful free development suite that can be downloaded from Atmel from here.
As I mentioned a while back I have had a C compiler and development and programming tool chain set up for a while now but I hadn’t got around to working out how to debug the code.
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.
I’ve been testing the new leg with one power supply for the servos and one for the electronics and all is working well. I expect that all would be working well if I were using a single power supply for both, as long as I was using the new one I soldered up and not the old one…
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.
Having decided that the graduated servo positioning method was the way to go to allow for leg sensors to work correctly I started thinking about leg sensors.
Here’s a new lower leg with three switches, one on the foot, one to the inside of the leg and one to the outside of the leg.
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.
I adjusted my quick and dirty servo controller program to calculate the number of moves required for the servo that needed to move furthest and then spread the movement of the other servos across the same number of moves.
