Tuesday, January 26, 2010

Two steps forward, one step back

Thanks to suggestions from Wade and NopHead on the RepRap forum, I found the problem. I feel like an idiot, especially when I am an electronic technician at work and doing pretty well, but completely missed the obvious on my own project.

It was suggested that I didn't wire up two extra lines from the I2C bus to the extruder board, which I did, and it still didn't work. So there I am staring at the firmware, and looking at the picture of the Mendel on the RepRap Wiki, when something clicked, verified something that NopHead mentioned, then looked at the wiring diagram closely.

Its true, i'm an idiot. The I2C isn't implemented at ALL, and the two lines that would actually send pulses from the mother board on what would be I2C to the stepper override pins, crazy huh?
So i'm pleased for a moment that the LEDs are flashing, except one.

I hooked up my DC motor with filter and on the side that had just one LED flashing, the DC motor did nothing, on the other h-bridge on the extruder board, it worked fine.

Another thing was, just in case, I put on a new 644p on the motherboard and removed the Sanguino 1.0 that I had bodged on, and using a specific command for AVRdude, which HAS to be run in the location of the hex file (something that people keep forgetting to mention) I was able to successfully program the bootloader, as was an old old problem where programming the virgin chip directly through Arduuino IDE first would always fail. However using AVRdude to program it the first time, Arduino IDE programs the bootloader just fine thereafter, weird. Another reason I hate Arduino, but not Atmel.

AVRdude come with the latest WinAVR install

The command I used, which I also posted on the wiki is
avrdude -c usbtiny -p m644p -U flash:w:ATmegaBOOT_644P.hex

Run under the directory

C:\Program Files\RepRap\arduino-0017\hardware\bootloaders\atmega644p>

Though with AVRdude, you can only use it through the DOS command terminal

There is a program that does it through GUI, I tried it, but it crashed and has not worked since

Even though I can't justify the expense of buying a replacement h-bridge chip for the extruder board, as local supplier Farnell is out of stock and means that i'll have to import it from far away, means that for a ~NZ$7 chip would cost upwards of over NZ$50 in shipping alone, but I still need my RepStrap done ASAP. Fortunately I bought a V1.2 stepper driver, essentially a L27/L298 combo that everyone knows and loves.

The H-Bridge chip is removed and modded the extruder board in a way that I can use the screw terminal to attach Step and Direction to the V1.2, though I have forgotten that I will also need power for it as well, and I have no spare plugs on my power supply, i'll fine some #8 wire somewhere and bodge it.

Monday, January 18, 2010


I'm quite annoyed from this past weekend, I still cannot get my extruder board to recognize commands sent from the host software to turn on the extruder.
My thinking is that I may have a dud chip, but I can't totally believe that, especially when I use Zach's test code which puts ADC signals to various parts of the board, yet though, when I insert my own code, which is simple digitalWrite, the extruder h-bridges are at 1.8V.
No one i've asked either cares or knows what is going off.

It is however entirely possible that I got a dud chip, I got one for the 644p, found the tx line 100 ohm internal short, how the hell does this happen.

I was going to post some pictures, but there is virtually nothing to see yet to make it worth while, all I have is a wooden frame, with the Y axis sitting loosley on top of the wooden frame, same with the x axis, though its lower down.
Both the X and Y axes are old, mismatched A4 flatbed scanners that I scored off www.TradeMe.co.nz for $5 for both.

I did buy another demijohn last week, hoping, and failed in the weekend, to transfer my wine to a clean and sterile demijohn so that all the dead yeast at the bottom won't affect the 3rd and final fermentation cycle, which could take 6 months or more, for my plum wine. Why plum wine? Cause I have a very large plum tree that fruits an amazing amount of fruit over every Christmas week, though last year it was 3 weeks early, great for getting me started for the first time on wine making.

Hmm, my blog posts seem to be rather long.

Saturday, January 2, 2010

RepStrap log start

I've started this blog, cause I feel like I need a place to jot down what i've done, and am doing.

To start off, even though my cartesian robot is about half complete, i've been working it for several months now, when I have either had enough money or time to devote to it.

I was hoping to have this thing built and working before the New Year started, so much for that plan.

So while its holiday time, and with the materials I bought at the start i've managed to get the inside frame nearly done for the z axis, just got to add a couple of bearings to it.
I'm designing the Z axis from scratch, the first attempt failed, in that it had way insufficeint constraints and mean't that it flailed everywhere when the threaded rod was turned. I am now using long drawer type slides attached to a frame, I won't know how this is gonna turn out till I get the outside frame done, that's the frame that moves up and down, the inside frame is stationry.

For the robot, the X and Y axes are made up of two old A4 flatbed scanners, bought them off TradeMe forNZ $5 for the two, what a sweet deal for two drive mechanisms, 2 opto end stops and high resolution 1.8 degree steppers.

I'm using MakerBot electronics, as there wasn't much point redesigning that which has already been done, though several people have apparently coded up their own g-code driver boards, if I get board I may try this by turning Adrian Bowyer's 5D Arduino code to true embedded C.