3D Robotics

ArduPilot MUX issue update: CKDIV8 fuse

We have now fully diagnosed the ArduPilot MUX firmware problem, and it turns out there were two problems, not one. The early boards were flashed with the wrong firmware, which was fixed on 1/26, but the boards after that until 2/5 continued to have a second problem, which is that the CKDIV8 fuse in the Attiny45 chip wasn't cleared at the factory, as it was supposed to be. What does the CKDIV8 fuse do? It divides the internal 8Mhz clock speed by 8, so the Attinys ship from the manufacturer with a default clock speed of 1Mhz. Our code, however, was designed to run at 8Mhz, so we clear that fuse to bring the chip up to its full speed. If you have an affected board, what should you do? Clear the fuse yourself with your AVR programmer and AVR Studio. Instructions are included in this post. Our apologies again for these teething problems, but I think this time we've squashed the last bug. All board shipping now have that fuse set correctly.
E-mail me when people leave their comments –

You need to be a member of diydrones to add comments!

Join diydrones


  • Please Guys I need help 

    I am working in Xplane with MP in order to SITL ,I followed all the steps in the manual but MP gives me this error below .

    What's the problem ? should I add something to my computer in order to get it done ??


  • Chris: Thanks, Thats good to know.
  • 3D Robotics
    James: Every Rx handles loss of signal differently. It appears yours holds last state. It looks like your ArduPilot is working fine.
  • Please can someone tell me how I would tell if the board I received in early February is affected? The mux appears to switch okay except if I power off my transmitter then it's always stays in the last state before before powering off the TX and I'm sure it should switch to failsafe. could be my receiver though. Thanks, James
  • 3D Robotics

    I'm sorry to hear that--I thought we'd stamped out these production glitches. Just to be clear, the CKDIV8 fuse was set on your AT45? (It should have been cleared)
  • I ordered an ArduPilot board from SparkFun on March 11, and it came with the wrong fuse value in the AT45. I had to reflash with open-source avrdude (using tinyUSB programmer from Lady Ada). See bcr's comments on page 5 of: http://diydrones.com/profiles/blogs/how-to-program-the-attiny-on
  • 3D Robotics
    Reto, just a note that the schematic and PCB files are always on our home page in Eagle format
  • @Simon: that's exactly what I needed to go on. Thanks very much, especially if you had to make the picture yourself. Somehow I forgot I could check out the schematic on Sparkfun ArduPilot page. Sorry for the inconvenience.
  • Hi Reto
    It's well worth studying the Eagle layout and schematics to be found in the Ardupilot home page but maybe this will help :

    The block of ICSP connections for the ATmega168 are exactly the same arrangement but shifted to the left hand block.
  • Hi all. I would like to know how the ISP pins are laid out on ArduPilot. I wish to know which pin exactly correspond to MOSI, MISO, SCK, RESE, GND and VCC of Attiny45. If anyone could give a schematics or a photo with labels, it would be perfect. My purpose is to build my own AVR programmer and I need to know this ISP pin layout to connect it correctly. Thanks in advance.
This reply was deleted.