XBase

XCore Project reviews, ideas, videos and proposals.
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wibauxl
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Post by wibauxl »

lilltroll wrote:Can you make some with 4 G4´s as well ? 8-)
:lol:
In fact, I am definitively looking at moving to a ONE L2 design for XBase, now that it is firmly out. This would allow for a great increase of power.
  • I just don't know what pins to expose (probably put the ADC and FT2232 and one 8bits port from one core and the Arduino connections and 2x8bits ports from the other core). I don't want to increase the footprint too much...
  • The BOM cost would go up 8$ (30%!)
  • I have not seen any 2 layers board out yet. So I don't know if the routing is feasible.


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lilltroll
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Post by lilltroll »

I bought a OKI hot-air device so I will be surprised if at least not I or Folknology will go for a try with 2 -layer design for L2. I have a very immature example here
http://www.xcore.com/projects/l2ulpi-2- ... gn-attempt
I usually paste some experiment cards on a PCB panel and I I will "soon" send away a panel for PCB manufacturing.
Probably not the most confused programmer anymore on the XCORE forum.
Light
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Post by Light »

It's a wonderful design. But why use 1M/12 bits ADC? Don't want to make bit depth higher?
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wibauxl
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Post by wibauxl »

Light wrote:It's a wonderful design. But why use 1M/12 bits ADC? Don't want to make bit depth higher?
The idea is to try to keep the total board cost not too high.
The chosen chip (ADCxx8) has several variants, all using the same footprint:
ADC088: 8bits 50KS/s..1MS/s
ADC108: 10bits 50KS/s..1MS/s
ADC128: 12bits 50KS/s..1MS/s
So according to the user needs, various chips can be soldered in.

It is always possible to develop a shield with a much faster/more accurate ADC...
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wibauxl
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Post by wibauxl »

Some news.
As said earlier, I went back to the drawing board to solve several issues with the XBase-L1 design.
Most features are kept. Here are the changes:
L1 -> L2
FT2232 -> USB3318
3.3V / 800mA -> 3.3V / 1500mA
1.0V / 300mA -> 1.0V / 1500mA
No power in -> JST connector
The board is almost routed with connectors kept at the same place.
I will post the result picture when done!
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bearcat
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Post by bearcat »

Just a couple hardware comments. Take these more as questions than any kind of suggestion or recommendation (they are not).

1 - Decided to buffer all except TDI for the JTAG?
2 - The XLINK's are very high speed. I would wonder if some R33's on those lines is prudent since they go off board.
3 - No connection of the USB shield via cap to ground? Or did I miss that in the schematics.
4 - I believe there is a 1K from Vbus to the USB3318 in the reference designs (I don't have the schematics handy to verify). Don't have the datasheet for that part so can't see what the manufacuture recommends or why it's there. No cap on Vbus line for the USB3318? Is the combination of R and uF's form a low pass filter for the USB3318?
5 - Having a max of 5.5V for power In with no protection seems risky. Lots of unregulated supplies that say 5V but may actually be much higher and a user not knowing the difference. Maybe this is typical with Arduino systems??? It would make me nervous.
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wibauxl
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Post by wibauxl »

bearcat wrote:1 - Decided to buffer all except TDI for the JTAG?
I merely follow-up on the XK1 design which sorts of make sense: buffer out the TDO and put some schmidt triggers on the clock-like inputs.
bearcat wrote:2 - The XLINK's are very high speed. I would wonder if some R33's on those lines is prudent since they go off board.
Yes, I know this is the recommendation for lengths of around 10cm. Since I only have 4cm with my board connectors, I thought I could avoid those. I suppose that I would lower the clock if I had some issues with the links.
bearcat wrote:3 - No connection of the USB shield via cap to ground? Or did I miss that in the schematics.
I have never done that on any of my design...
bearcat wrote:4 - I believe there is a 1K from Vbus to the USB3318 in the reference designs (I don't have the schematics handy to verify). Don't have the datasheet for that part so can't see what the manufacuture recommends or why it's there. No cap on Vbus line for the USB3318? Is the combination of R and uF's form a low pass filter for the USB3318?
I will check this. I sort of followed up on the design of the XTAG, assuming that XMOS had done their homework on a key piece of their development chain!
bearcat wrote:5 - Having a max of 5.5V for power In with no protection seems risky. Lots of unregulated supplies that say 5V but may actually be much higher and a user not knowing the difference. Maybe this is typical with Arduino systems??? It would make me nervous.
Yes, you are right. I guess I am using in most cases USB as a power, so no problem.
I will have a look again at alternative regulators with wider input ranges. The one selected has a good price though and absolute max of 7V. Reading the data sheet, I just realized that the minimum voltage for input is 4.5V, so not too good for battery input. So another candidate is the LM2734 which is just twice as expensive...
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Post by kster59 »

I would go back to the original design and use an FTDI chip instead of the 3318.

Have you (or anyone else) used the 3318 successfully for any kind of project? It seems that is only 1 driver for USB audio and that works only if you buy the special USB audio XMOS L1 chip with min qty of 160.

At least with FTDI you can have some way of doing useful work instead of just a chip taking up space with no driver support.
bearcat
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Post by bearcat »

Choice of power supply is tough. I have not found a small and cheap switcher that was more than 4.5 - 5.5V input. Using the national part is much more expensive and much more board space as the inductor is large, along with the need for a diode. I have used a compariable On-Semi switcher that is 1/2 the price of the National before with very similiar specs and components.

With a rectifier in the path, that makes the 4.5V low limit pretty tight.

As an interesting note, XMOS changed to a Semtech SC4626A on the v1.2 rev USB audio board for the 1.0V regulator? Appears to be a fixed 1.0 regulator, so no need for adjustment resistors. But I have no idea where anyone whould buy this part? Only a total of 5 hits on google for that part and I could not find any vendors (outside of Asia maybe).
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wibauxl
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Post by wibauxl »

kster59 wrote:Have you (or anyone else) used the 3318 successfully for any kind of project?
No, and I have been searching he web for quite some time to find some details about ULPI in general, with no luck. I was under the (obviously difficult to verify) asumption that this ULPI chip would allow XBase to appear as either a CDC, MassStorage or Audio USB device...

The documentation around the use of ULPI is VERY scarce from XMOS. In fact, apart from the design of the Audio card and one mention in the hardware recommendation, nothing...
There must be some kind of hardware flag to set up ULPI and dedicate the pins to that function. And XMOS must have some kind of library to deal with ULPI. This IP is probably burned in the OTP to deliver the USB functionalities.
I find strange that XMOS do not provide a guide to this ULPI...
kster59 wrote:I would go back to the original design and use an FTDI chip instead of the 3318.
Strange that you said that, I was wondering exactly the same thing!
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