Jun 252012
 

I made these little boards for the excellent TS-7500 from EmbeddedARM. It’s a small little ARM processor that runs linux.

My board breaks out all 8 XUARTS, 4x RS232 and 4x TTL serial ports, and some other GPIO’s to headers, I2C too. There’s space at the top for cable ties to make sure cables can’t get yanked out.

Assembling then was easy enough, I got the the PCB and etched stencil done at PCBWing, and the quality is very good, as per usual. Most of my passives were 0402 (because I LIKE PAIN!), and the level-shifters for the RS232 are the 1-mbps capable TRSF3232E.

As you can see, the passives are TINY:

And, yeah, I forgot to bring out the Console out to headers, and, instead, I put LED’s on them!!! Idiot!

And it works! That’s a Seeed Grove Serial LCD.

If you want the eagle files, let me know and I’ll post them up!

May 212012
 

Or “dq” as I am calling it.

It’s a dodgy little quadcopter I’m building with available materials here in the remote “city” of Swakopmund, Namibia, which is where I’m living for the moment (for work reasons).

There aren’t many building materials for a machine like this. I managed to find some 10mm spruce, which I believe have been sitting in the local toy & hobby shop for the better part of a decade. I’m using them for the “arms” and motor mounts:

I did some electronics testing, I connected the motor to a Turnigy Plush 18A ESC, to the receiver to the battery and hit full throttle:

I also tested how much thrust I’m getting using a super advanced method:

I was getting about 370gr on 50% throttle and 800gr on full throttle, which I think is fairly reasonable. I would love to have a current meter to see how many amps i’m actually drawing.

As for the frame… well, it’s a little on the heavy site, but I’m working to lighten it:

Yes, that’s something from the plumbing section at my local (and only) hardware store!

Here’s a pic of the basic framework:

 

Jan 222012
 

So, I got my boards back, got the components ordered in, and I’ve assembled a couple of them.

They don’t work.

Kinda. The micro runs whatever code I put on there, the LED’s blink if I tell them to, but it doesn’t like the USB part. I plug it in, and my computer chucks a dummy spit saying that the “USB device is not recognised, bro”.

I got it working on the breadboard, the exact same code. And apart from a few extra LED’s (that aren’t currently turned on), there’s not much more to the circuit. I have verified all traces, all paths, checked for any bridges, etc. I just don’t know what’s going on.

I’m posting this up to see if anyone can help me debug the sucker and maybe tell me what’s going on. I’m including the schematic, the board layout, the eagle files and a high-rez photo of the current state of the board.

Note, since this board is Rev1, I know I screwed up a couple of things. Most importantly, the 1.5k resistor, R5, should have been connected to the D- instead of D+, that’s been fixed by soldering R5 directly to the “correct” place. Also, the ISCP header, I’ve mislabelled GND/VCC (I know, I know!), so on the board it’s crossed out (but the pins are in the correct spot). I’ve put 22pF capacitors for the crystal instead of 18pF as a different test (this is the second board I assembled to rule out “burnt component” issues).

Here’s the deal. If you are able to point out what I’ve done wrong, I’ll send you one of my blank PCB’s.

Schematic:

Board layout:

Populated board (no switches):

Eagle Files:

uKb_v1.1

Jan 132012
 

My boards are here!!

This is going to be a “utility keyboard” – uKB.
4 buttons and one rotatory encoder, plus 6 PWM’d LED’s. All inside a nice bamboo box. It implements standard USB HID, so it should be plug&play on all computers. You have ISP header for the atmega328p, for changing firmware, and I’ve brought out all spare pins to a spare space on the lower right.

The thing is, the boards arrived on a friday afternoon, and i wasn’t expecting them until monday, so I don’t actually have the components to populate the board! I guess that will have to wait until next week!

Jan 082012
 

I’ve been thinking about creating my own LiPo charger for a while now. Something that will allow me to charge a large array of LiPos in the field without it been fiddly or annoying.

Since I now know a bit about electronics, I set out to see what it would take to make a simple and modular single-cell LiPo charger. Something based around the MAX1555 or the MCP73831. I chose the Microchip one because I liked the fact that the datasheet had a recommended layout for the PCB tracks to improve the thermal properties.

For the daisy-chaining, I’m using these cool hermaphroditic connectors from TE. They handle up to 6A, so it should be good for a few chargers in one chain. And they’re only 79c!

For regulation, I’m using a Murata switching regulator to get from Xvolts (where X can be a car battery) to the 5V the lipo charger chip likes (thanks Kean for the suggestion!). They’re not terribly cheap, but they’re efficient and kinda small.

I’ve also put on one end a USB socket to allow charging of a single battery off USB. There a lot to be improved in that corner, and I don’t think it’ll be the primary usage, but in a pinch it could be very handy. Since USB only allows 100mA draw without negotiation, I’ve laid out an ATTINY there to act as a USB device that wants more power. There’s a lots of suggestions flying around, like, put a fuse there (Madox, Jaye), and they’re all good ideas, but I haven’t gotten around to implementing that yet.

All of this experimental, of course, but this is the fun part!

Schematic:

Board Layout:

Download the EagleCAD files here: MCP7383_v1

Sep 212011
 

And even before I get my other PCB’s back, I’ve already sent of new ones to get fabbed! I got these panelised because they will be going to an assembly house to get professionally made up.

This is quite exciting.

Sep 172011
 

Proof of concept works up to 921600 baud over these many dodgy cables, hand soldered dead-bug prototyping on the 1206 caps and wire into wire into wire. I’ve finally started actual electronics work at actual work, and this “board” will be fabbed next week as a final product, first with a run of 3 reflow-skillet soldered prototypes, and then an initial run of 20 or so, and, depending how many they break, I’ll get more assembled.

For those that are wondering wtf it is, it’s a basic high-speed USB-RS232 converter, very very simple, but I haven’t been able to find one commercially that does 921600 baud, which I need.

Sep 142011
 

Here is my 1st board reading for fabbing.

I’m getting quite nervous about making sure that all the footprints are correct, that the traces have correct thickness, that the impedance is enough (I have no clue about this), that the dimensions are right.

I just realised that I should put some sort of mounting holes on it! Could be important!

Sep 082011
 

It took long enough, but I finally have some free samples!

They are some Mill Max test pin headers, 2×4, with 1.27mm pitch, which is nice and tiny!

I’m glad I managed to get some samples, mainly because the minimum quantity I could find them in is 98, and at $11 each, that’s quite step, especially since I only really wanted 2 of them.

I’ll be using them as ICSP headers or maybe JTAG (JTAG fits on 8-pins, right??)

UPDATE:

I’ve received more samples! This is fun!

  • 2x 28-DIP ATmega328
  • 4x 32-TQFP ATmega328
  • 2x 100-TQFP ATmega2560
  • 2x 44-TQFP ATmega644
  • 2x 40-DIP ATmega644 (not pictured)

I’m kinda kicking myself for not having asked for some AT32UC3L’s too, since they are hard to come by in Australia and I don’t want to pay $40 shipping from the US. And, also, I’m going to be using them for my next project.

Good thing that I kept the 44pin->dip converter board samples that I received last year, since I can use them on the 644, though since I also have the 644 in a DIP package, it’s not that important.