L'Hexapod

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. As I mentioned here, there’s a fundamental design problem with the two versions of the ATTiny2313 servo controller firmware that I’ve presented so far (see the 8 channel source code and the 64 channel source code). The timing that determines the shape of the PWM signals that are generated relies on carefully crafted timing loops and the time taken by particular code sequences and this is affected by the interrupt driven serial I/O that is used to control the controller.

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 rather nice; Chiara Robot from Carnegie Mellon University’s Tekkotsu lab (via HackedGadgets.com).

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 are some links that may help once I move onto fabricating the various pieces required to build the hexapod’s body. This is a simple 4 legged walking robot that was machined from an A4 piece of 4mm ply wood.

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. A collection of links that I’ve been using recently for research. Servos and robotics Hitec HS-422 Servo. The servos I currently have; likely not suitable for use as actual leg servos due to lack of torque. Useful link as www.

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.