If you get your own PCB's made when the design files are available, you can just fit the components you want, bridging out the RS485 driver will let you still use the serial channel, but at logic-levels.When I release the files, the PCB artwork will be in a zipfile, just email it to seedstudio, pay the low fee and a few weeks later your very own batch of 10 boards will arrive.There are refinements I want to make for a next version, perhaps a LED on the board and a reset button. I really want to keep to 1206 resistor/cap packages as for home assembly they are quite manageable, and to keep away from the tiny sm footprints as I just cant work with them. I did have to resort to three 0803 components, the xtal caps and a ferrite bead.Perhaps some solder bridges for power and 2nd serial options. I'm trying things to see what I can fit.At this point, I dont have any way to sell these, or even have an idea if people would want them. I made these with my requirements in mind, ie the RS485 port is not a common requirement. I can probably make it optional (bypass the chip) so in that regard its more generally useable.So I'll just keep on with the testing and trying to fit any modifications I can think of (or are suggested)
I was lucky enough to be one of the Goldilocks backers, I cant wait to get mine.Its in a completely different class from my effort. It is a very well engineered board and a huge amount of effort and thought has gone into it to make it one of the most 'serious' Arduino's I have come across, suitable for complex and diverse applications, even using the two CPU's for independent programs and communicating between them.
I just thought of the bits I wanted, crammed them into a small space and figured its worth a try... If its a dud then its not the end of the world. If it all works then happy me.I just like making stuff
I've built up a few boards now for testing purposes, The 22M version is one of them.On digging into the Arduino code for the problem with the delay() times, from what I can see (and I'm not really a software person), it looks like the delay code is only going to produce valid results for 8 or 16Mhz. Anything else will give wrong results. This is a bit of a pain. Its probably fixable but this will involve modifying some core files and I'm not too keen to go down that path, and not really sure how to. 22.1184Mhz is good for accurate baud-rates and loading at 115K, but a non-friendly number for deriving a 1ms counter.I'll live with it for now as its not a show-stopper and everything else seems to be good. 16Mhz is fine and Arduino delays work as expected.
I got a batch of 1284P's from Mouser, + assorted other support components. This will let me make up the basic boards without the extras and have some available if people want one.
I tried codeblocks but it seems to have issues running on my XP virtual machine. Took ages to load and each time I tried to do anything, there was a 20~30 sec delay before anything happened. I'll stick with AvrStudio for now.
I did change the 'board type' for the different frequency builds. I loaded a basic sketch into the different frequency boards and then looked at the disassembly in AVRstudio.There are assumtions made about the clock frequency (either 8 or 16M), which is fair enough I suppose as thats what Arduino's run at. I'm not too bothered about it for now and if it gets to the stage where its a problem then I'll look at (trying) to do something about it.
I do use the basic libraries for Kicad, but each time I make a new component, I add it to my own library so it has grown over time.I looked at going the Eagle way some years back but did not want to get locked into a system that was limited in the 'free' release. Kicad has no restrictions in that sense.Its not as 'seamless' as Eagle, but its quirks are not such a handicap that I cant live with it.I have not experienced the problem that you describe, but the releases are regular so whatever it was may not be there any more.
I think I have arrived at a 2nd build version now.It has more flexible power options. Positions for two regulators on board, a 5V and a 3.3V.With the two power rails on the board, the micro (and RS485 if fitted) can be run at 5V for full speed. The other items all run a 3.3V. The 5V rail can be connected to the 3.3V rail (with no 5V reg fitted) and the whole board run at 3.3V. Also now fitted,A power LEDA LED on one of the I/O pinsA reset buttonThe radio connector is now the cheap nRF version as per ebay (and many other sources)Ground-plane beneath the battery (for the RTC) is fixed and the 32Khz xtal footprint fixed.The PCB is done, I just need to check it over for a few days and see if I spot anything wrong then I'll get a batch made.Its 5mm wider so still well within the 50x50mm PCB area at Seedstudio (and others)Since I'm ordering boards, I'll do a RFM12 adapter that fits onto the radio connector, I use both.If it all works OK then I think that will do for me. I'll release the files and anyone can do what they will with it Schematic now attached (you need to log-in to see it)
I used a ferrite bead because of some comments on the Goldilocks Google design docs page. I thought I'd give it a go. I have always used basic inductors so far but I'm willing to try and see. In my layout it may not make any difference as its hardly set out for optimum analog performance. On the plus side, it uses linear regulators so that will probably help.
I use the 10u caps because I have a stack of them. In the Wiznet forums, good decoupling on the wiznet module seems to be fairly critical. I also wanted to keep to a 1206 footprint and I did not want the package height to be too much, so multiple smaller devices.