Minimig PCB run - interest thread

[Hans_]

jkonstan wrote:
What could be different and may cause an issue between these SRAM parts is ground/VCC bounce since the PCB is only 2layer and lends itself to a higher inductive volatge drop Ldi/dt on the power and ground connections to the ICs. We can only tell this by testing some of these SRAM parts in an actual 2layer MiniMig PCB.

Sticking a decoupling capacitor right next to the SRAM chip should solve this problem. If the  Most datasheets have some kind of recommendation for decoupling/circuit-layout that you can follow.

Hans

[jkonstan]

The decoupling cap next to the IC will help VCC dip/bounce; however, it will not help with ground bounce. Ground bounce is fixed by use of a low L inductance ground path connection for the IC/SRAMs (i.e. a ground plane).

 :-)

[freqmax]

I have noticed that digikey.com have started to stock the XC3S400-4PQG208C at 25.45 USD for one off:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=122-1519-ND

They didn't before. So it was a real pain in the ass to get those chips at reasonable ease and price.

[koaftder]

The joys of sourcing parts. Here today and gone tomorrow, or worse, company lies about having them on hand and missing deadlines.

[CD32Freak]

Here are some interesting links for those who want to make their own minimig PCB:
Make PCB's with a laser printer
Easy PCB Fabrication
Express fabrication of pcbs from gerber files
:-D

[Nusim]

We have a small run of original (Minimig ver. 1.0)bare PCBs.

The only change is the silk screen just to identify the source for quality control.

I stress that these are suitable only for the serious electronics dudes, experimenters and people interested in 1st wave prototypes. They will involve smd work and so are not for the faint hearted!

We are expecting them in next week. As soon as they arrive we will post a link to a paypal shopping cart.

Pricing will be;

£11 - Shipped U.K.
£13 - Shipped Europe (Airmail)
£15 - Shipped World (Airmail)

We will also try to source the original ST memory and make those available as well.

Any profit will be donated to the TeamAros Kickstart II bounty! :-)

[koaftder]

CD32Freak wrote:
Here is an interesting link for those who want to make their own minimig PCB: Make PCB's with a laser printer :-D

Been there, done that. Heat and pressure often smudge the traces on the qfp tracks, thin tracks often get lifted off the board when removing the wet paper, etc. Applying heat and pressure uniformly is difficult, the larger the board, the higher the incidence of over pressure and heat on some spots, under pressure and heat on others. Some traces smudge, others don't stick. Getting the top and bottom layer aligned right will make you go postal.

Yes, the minimig is pretty simple, but I wouldn't bother trying to ghetto fab the board. It would be cheaper and less stressful to get it done right.

[koaftder]

Nusim wrote:
We have a small run of original (Minimig ver. 1.0)bare PCBs.

The only change is the silk screen just to identify the source for quality control.

I stress that these are suitable only for the serious electronics dudes, experimenters and people interested in 1st wave prototypes. They will involve smd work and so are not for the faint hearted!

We are expecting them in next week. As soon as they arrive we will post a link to a paypal shopping cart.

Pricing will be;

£11 - Shipped U.K.
£13 - Shipped Europe (Airmail)
£15 - Shipped USA (Airmail)

We will also try to source the original ST memory and make those available as well.

Any profit will be donated to the TeamAros Kickstart II bounty! :-)

That is good news, but I wouldn't buy the PCB without the parts kit as well. Buying the PCB and then sourcing the parts from 3 or more vendors would make the cost prohibitive in shipping alone...

[Plaz]

it's as in 'AROS roots'... I was told that it would be it's as opposed to its by an US speaker, but I had that very same doubt as you.

To clear this up.....
it's = the contracted form of "it is"
its = possesive pronoun, belonging to

This seems contradictory even to native english language folks because MOST of the time the 's is tagged on the end to show possesion. Not in the case of the word "it".

So in Pixie's case the correct usasge would be "its roots".
(Notice the contradiction in the previous sentence?)

Now back to minimig.... I've update my preference.
Mini or microATX is fine as long as we can stick to a standard.

Plaz

[odin]

Methanoid wrote:

odin wrote:

"It's" and "Its" are both valid possesives in English AFAIK.

No, they are NOT!!!

Indeed you are right, I stand corrected =).

[jkonstan]

Nusim,

The MiniMIG pcb 1.0 run sounds good to me.
 
I am interested in a MiniMIG blank pcb 1.0, and I am one of those serious electronics experimenters.

Please let us know when these become available.


  :-)

[Hans_]

jkonstan wrote:
The decoupling cap next to the IC will help VCC dip/bounce; however, it will not help with ground bounce. Ground bounce is fixed by use of a low L inductance ground path connection for the IC/SRAMs (i.e. a ground plane).

 :-)

Actually, it helps with both VCC dip/bounce and ground bounce as it provides a low-inductance path for transient currents on both sides. If you draw out the circuit schematic for a decoupling-capacitor connected to an IC, you'll see that it affects both VCC and ground.

A ground plane is still a good idea. You should be able to create a reasonable ground plane on a 2-layer board if you keep most signal lines on one side and keep any signal traces on the lower layer short.

Hans

[billt]

Been there, done that. Heat and pressure often smudge the traces on the qfp tracks, thin tracks often get lifted off the board when removing the wet paper, etc. Applying heat and pressure uniformly is difficult, the larger the board, the higher the incidence of over pressure and heat on some spots, under pressure and heat on others. Some traces smudge, others don't stick. Getting the top and bottom layer aligned right will make you go postal.

What about photosensitive bare boards and printing to transparencies for exposure?

But yes, I'd agree that having it made by a real manufacturer would give best results.

[freqmax]

The toner-transfer method: http://max8888.orcon.net.nz/pcbs.htm

Might be useful for throughhole, small boards.
But this is many components, highdensity, doublesided board. I think that requires proper methods.

[Hattig]

Definitely interested in a working minimig board.

I think it would be good to not rush into this - the sources have just been released, so let's see if we can save some pins on the FPGA for future use (I liked the suggestion to use the larger capacity FPGA that still had pins but had more usable pins available, but I'm sure there are good reasons not to use it). On the other hand we don't want to wait forever and future enhancements can be turned into a new product revision (the second run of boards).

Is the reason for the SRAM so that the design doesn't need a memory controller for SDRAM on the FPGA (which would require a huge bunch of pins)? It would have been nice to have 8MB, but not at the price of the SRAMs.

I'm all in favour of the smaller board, tweaked to have a nano-iTX compatible layout myself.

Could be cool to use the product to try and implement other computer systems too - the Atari ST comes to mind immediately (although it has a slightly higher CPU clock that could prove an issue with the current design) as well as a host of 8-bit computers (with their CPUs implemented on the FPGA). So being able to select which 'system' to load in the beginning would be awesome, if that is possible from the SD card...

[ivier]

hmm, could probably use PSRAMs... they are supposed to be as easy to interface as SRAM, but offer the capacity and price of SDRAM.

i personally like the idea of headers instead of ports, and would prefer a pre-assembled board (my soldering skills need more work, SMD is still out of reach for me).

A larger capacity FPGA would be nice, but not necessary.
the actual form factor, i don't care about, as long as it's still small.
I'd like at least an 020, but thats not really important for a first run.

All in all i definitely want to get one.