I just put the finishing touches on a development board for Luminary Micro's LM3S3651 chip. Luminary is now part of Ti. I love the peripheral library that comes with them it makes them really easy to use, particularly for ARM microcontrollers.
Basically I designed the board with USB Host or Dev applications in mind mainly. Mostly I wanted something that could do hosting of power hungry USB devices (like hard drives), but it is good for much more than that.
It is Cortex M3 128 KB Flash, 32 KB SRAM, 50 MHz, 29 GPIOs, SPI, UART, I2C etc.
Anyway I just wanted to start a thread for anyone who needs help using it. Though I wrote really comprehensive docs I think: http://teholabs.com/docs/eridani:overview
I go over setting up both serial and JTAG toolchains. I plan on full support for the BusBlaster when it is in good shape.
My next big project is probably going to be this idea, I am just interested in if anyone else here is interested in the concept.
The basic point is a modular very high quality music player for your home.
Basically the structure will be a Cortex M3 with a I2S interface to your choice of DAC backend.
The M3 micro will have a bunch of SDRAM for you to have for scratch decoding space in which is directly accessible in the memory map. For storage it will use FAT on a USB mass storage device. Say a 2.5" hard drive.
The uC I think I will use is a LM3S9B90 but I also might use a LM3S9790 for this project.
These have built in Ethernet but given the 12 MBit rate of USB Full-Speed to the mass storage I don't know if that is really the best transfer means, probably a pull the disc add files scheme is better.
The project may have a daughter board for the user interface/display to let people choose the display they want to use. This way if someone wants to do touch they could or what have you. My inclination is for VFD + a few buttons and a rotary encoder.
My codec priorities are: WAV FLAC OGG anything else
I don't think there will be MP3 support for licensing reasons, some sort of computer side transcode might be the best workaround for large MP3 collections, but as the point of this is HiFi hopefully the sources are better than average MP3s anyway...
The first DAC backend I have planned is WM8740 based.
I have no issue with 0805 or even 0603 just fine pitch stuff. I don't know what you mean by mix, my paste is just in a jar, I spoon some out and let it warm up then apply. (NX01 Kester).
I would say the load dictated by the stencil for the fine pitch is too much, and too little for big stuff, so I should use a thicker mask with smaller apertures everywhere but the big stuff. That would load everything correctly.
Interesting tips, I don't know how I could get a reasonable amount of paste without quite a put of pressure. Saw a video of Sparkfun production and they used a metal Spackle knife. I tired the rubber squeegee first, I had the best results with a plastic putty knife. I feel like the slots in the stencil are just too wide really the paste slumps enough and there is too much overall... The problem would be fixed if they were 30% smaller because ever other place on the board needs *more* paste. I have a lot of issues with pins pulling on high force headers because I used so little paste, it means I have to check the boards a lot to make sure they are perfect.
I actually have found that while it may be too much paste for the TQFN it is too little for the bigger parts... I am getting better at it with some flux I can unbridge it okay with a bit of work...
You probably just need the "Install and setup Cygwin, OpenOCD, and other utilities" section.
You can hack my makefile and linker to your device when I post them I think. But that stuff needs some cleanup before I am done, and I am busy for the next week.
Yes only the connectivity line supports I2S (and the performance XL devices) with good audio accuracy and has USB hosting. Connectivity line does not have an external memory interface.
This is more or less along the lines of what I suggested to free the B port for UART. Glad to see others have the same thoughts. If I know Ian there will be more revisions. Hopefully all the best ideas will merge back together.
For low cost projects this doesn't make good sense to do because the shipping cost for a Mouser or Digikey order is more than the savings. Also the unit 1 cost vs the unit 100 cost... You are right that it is busy work but you could mail many projects for under 1 dollar in first class mail.
Look at eevblog.com he had a big long video on PCB design and that is what he does for a living. It seemed good advice. Screaming circuits has a PDF on what they require. Basically you need fiducials and a place around the edge of the board for the tool to hold the board. You need to give detailed BOM and part cord/orientation. KiCad does this and I am sure Eagle and others also do... You need to use long tapes or tubes for everything (no bulk), some people need everything reeled which is more costly for small runs...
That is all I know for now. Basically I haven't found an house that will build like 25-100 of something for cheap enough to make it worth it. 5-10 dollars a board for a simple design is in quantity of 100 is about what I have found. Houses in China I have found only do 1000s of dollar volume stuff. If you find a nice house to do cheap short runs let me know!
Would you be willing to be open about what kind of margin you get on these seeed studio stuff? I mean the break out for the MCP2200 only should cost about 1/3 raw parts even in very small quantity. So is seeed getting all that money for the ASM or are you getting a significant fraction? You need not say exactly what is what but I am curious as I am going to start selling parts soon and don't actually enjoy the assembly process.
[quote author="ian"] In other news: I'm afraid we're going to come to the conclusion that this board won't be routable on 2layers in the space allowed by Eagle free... That doesn't mean it can't be done, just that it isn't feasible with our resources. [/quote]
I think you should start using KiCad. It is pretty easy to use, no limitations like free Eagle.
I will probably release a Luminary based board that could run linux easily sub 100 dollars later this year. (Though I don't plan to use linux on it myself at this time, it should have between 8-64 MB of SDRAM).
