Missing RAM Pins

Unfortunately they are connected in the eagle file.

It would be possible to disconnect them as the trace joining the two is accessible on the bottom of the board, however you would still be left having to run a wire to bring the NRD pin out.

So really, unless you can set the A5 pin to be an input, and then use the external memory with structs which contain a maximum of 32bytes, and store those structs in the memory aligned at 128byte boundaries, then sadly the external memory capability is not possible.
That right there severely cripples the Due's capability and the number of possible uses for it.

Graynomad:
I would also vote for a format that doesn't use 100% of the edge real estate for the backplane, there's hardly anywhere to put your own connectors.

@Graynomad:
What do you mean by "100% of the edge for the backplane" -- the double-row header socket at the right edge? But if so, isn't that part of the standard Mega format -- and thus all corresponding shields, for those who want to use them?

What I'm saying is that there's no room left for connectors on my shield should I want to make one. For example maybe I want to make a shield with 4 or 8 serial ports all using DB(DE)-9 sockets. Where do I put them?

Granted that's hypothetical and nobody else is complaining :slight_smile:


Rob

With the Due you can put them at the USB connector end now that they have switched to uUSB :stuck_out_tongue:

now that they have switched to uUSB

At last. Yes you now have about 15% of the edge to use.


Rob

Use SMD pin headers on the side of the shield facing the Arduino board and use SMD DB9 sockets on the other side. E.g. Harting makes SMD DB9 headers.

True, if you use SMD connectors you have all the edge to work with as long as you're happy to have the board at the top of a stack.


Rob

I hate to bump a thread, but does the team have any comments on this? I do understand that mega compatibility > RAM/ethernet support, but for Arduino users who need the extra memory, is the only solution for the foreseeable future (6+ months) to either a) roll your own board or b) use the Atmel evaluation kit?

is the only solution

I think so. Officially, none of the Arduino platforms has ever supported add-on RAM (the add-on boards for the MEGA are all from third parties...)

Officially, none of the Arduino platforms has ever supported add-on RAM (the add-on boards for the MEGA are all from third parties...)

At least it was possible with the Mega, the Due doesn't bring out one of the address lines (A6?) so you're screwed.


Rob

So I've been looking into the SMC as well for an LCD and for what I can gather, since I don't use the ADDRESS pins for address, it seems I could still use the SMC to write to my LCD. It's using 8-bits. I do need ONE address line to tell it which memory internally to work with. Although I am not 100% sure. Still porting code from a Mega2560 project.

I think you'll be right there, the SMC has almost all the pins brought out for 8-bit access it's just that one address line so should be right.

If you do this let us know how it goes.

Of course one might wonder why you need to use the SMC for an LCD, LCDs are normally as slow as a wet week so memory-mapping one wouldn't help I think.


Rob

Looks like a good opportunity for a third party vendor to create a board using the Due's chip, but wired up for the hardcore extreme user. Rather than cloning the Due, it'd be an innovative evolution.

Looks like a good opportunity for a third party vendor to create a board using the Due's chip, but wired up for the hardcore extreme user. Rather than cloning the Due, it'd be an innovative evolution.

I actually did just that when they first announced the Due, had the PCB laid out and everything. But I used the 3U because that's what they said they were using. Then they changed to a 3X and I didn't have the energy to re do it :slight_smile:

I brought out ALL the signals (IIRC) with a form factor that allowed a lot of the board edge for user connectors and various modes that allowed addressing on the backplane etc. It also used the great power control ability the SAM has to shut down the board and save power. Plus it could control about 6A of external power.

Here's a render of the finished PCB

So yes, I think there is an opportunity for a bright young lad to make a "pro" version.


Rob

Rob, that is not only beautiful but impressive as it gets.

Thanks, it was pretty packed, 2.2" sq, 4 layers with almost as many components on the other side IIRC.

Shame to wast all that time, maybe I should re-jig it to use the 3X...I feel exhausted just thinking about it :slight_smile:


Rob

If you do re-do it, should toss in the ethernet jack while you're in there. How different is the pinout between the 3X and the 3U?

should toss in the ethernet jack

A problem with this is that it's not just the ethernet jack. You also need an ethernet PHY chip, which usually has its own crystal, and a relatively "serious" interconnect to the main CPU...

Yes I think Ethernet wouldn't fit, maybe I could squeeze in 1 or 2 more resistors :slight_smile:

@UnaClocker
I remember it was enough to force a complete redo of the PCB, but I'll have another look.


Rob

The 3U and 3X are totally different pinout wise so it's a complete redesign of both PCB and partial redesign of the schematic because the 3X has at least one extra feature (the DACs).

So unless there's some real interest (unlikely) that's all folks :slight_smile:


Rob