I don't know anything about electronics but I've heard that memory is one of the most difficult components because
it uses wide, very fast buses, and any slight discrepancy in track length or width may cause problems (maybe to one
chip and not another). Also, at least for PCs I've heard getting RAM timings right is also very tricky (but it may be
2x or 3x the Hz than the Pyra). And you can't really be sure they work until you get the timing right in u-boot (or the kernel?).
The other risk is if the 4GB chips draw more power than 2GB chips, and that somehow requires some change, but I'm not even
sure, since it's 2 chips for 4GB and 4 chips for 2GB. They might even draw less power ? No, I guess it's still double the bits
to refresh periodically but what do I know?
Well, it was a misunderstanding by me that the 4GB chips would only be 2. They will also be four, and they are pin compatible.
RAM is not so difficult, actually. Yes, you need to make sure your bus is compatible with the RAM, but that can be checked upfront.
So we know the RAM should be compatible. Power supply is not a problem here as well.
The Pandora actually had three or four different RAM / NAND-Chips during it's lifetime, and every chip needed an update of U-Boot (to include the timings and set it up properly).
It never took too long.
With the 4GB chips, it's a bit more complicated as we need an LPAE kernel. But that's not impossible.
So I wonder how long this will take. Having it working with 2GB is a hint PCB changes may not be needed but I'm not
sure it can be completely ruled out. In fact having the board designed by Nikolaus is an even surer hint no changes
will be needed. So I'm not really worried, just not so confident it'll be sure enough in a short time. Let's hope so.
Yes, it's 100% sure no PCB changes are needed.
I somehow thought there was one prototype already built with 4GB from this june posts.
Yes, one CPU board had been reworked.... but only with 2 of the new chips.
So it's a frankenstein board, with two old and two new chips. AND it's reworked, so we don't even know the hardware is 100% intact.
So not the best board to try to get the software to work.
It's better to wait for real produced prototypes.
That's what's more lovely in this project, hard work, no rushing and transparency.
I trust you won't order the 2000 prototypes until you're sure they'll work with the 4GB RAM.
At least not the RAM chips, as that would be deadly
As said: there's nothing in the board design that needs to be changed that make the RAM chips compatible.
All traces are within specs, the RAM chips are pin compatible.
Maybe it's not worth it rushing for Christmas. If it's for Christmas fine, if it's for New Year's Eve fine, if it's for FOSDEM, fine...
This is great hardware, let's not risk a flaw for rushing.
Of course there's on need to rush for christmas. But it would've been nice!
I didn't know it was needed. Sounds even better with it, but I thought it was said the Pyra was already cooler than other similar size devices ?
Will it be for the battery or the CPU board ?
Well, cooler than even faster devices: Yes. But that doesn't mean it can't heat up.
Also, the OMAP5 is an older SoC. So even though it might not heat up as much as the Intel, it heats up more than it compared to the processing power.
So having something to keep the SoC a bit cooler for a while is a good idea, and it will only cost a couple of cents.
I think I'm going to be silly as hell since I know nothing of electricity, electronics, electromagnetism or radio.
But if the resistor value depends on the distance to access point or environment where the Pyra is put, would it make sense to use a potentiometer instead of a resistor
and let software control it so that people can maybe experiment for best setting in different places ?
Not quite. An antenna needs to be setup properly in order to receive the correct wavelength (i.e. 2,4GHz or 5GHz).
An antenna is basically just a wire from the Wifi chip to the battery, but that "wire" is laid out in a way that it receives the wavelength as good as possible.
However, between the antenna and the wifi chip, there's a trace on the PCB. That trace changes the resistance of the antenna, so the reception is not as good as it could be.
To compensate that, you add additional resistors between the antenna and the Wifi chip.
What we need to do is find out the optimal resistor value for the compensation. This can be done by measuring the reception quality of a Wifi signal under the exact same conditions each time while changing the resistor value.
Simple example (resistor values are just made up here):
With a 500 Ohm resistor, reception is -20dB.
With a 600 Ohm resistor, reception is -30dB (so worse).
With a 450 Ohm resistor, reception is -25dB (so still worse than with 500 Ohm).
With a 550 Ohm resistor, reception is -15dB (so better).
With a 525 Ohm resistor, reception is -18dB (so worse than the 550 Ohm one)
With a 535 Ohm resistor, reception is -12dB (best value so far)
With a 540 Ohm resistor, reception is -14dB (getting worse again)
With a 538 Ohm resistor, reception is -11dB (best value).
So you change the resistor and narrow down until you find the best reception.
Then you know the resistor for best possible reception. That value doesn't change, it depends on the board layout.
This is a very simplified example, but I think it should be easy to understand.
Of course, reception also gets worse when you move away from the access point, but that is not being compensated with resistor values but with increasing / decreasing the Wifi power (which is what the Wifi chip and the router does automatically).
Sorry for my ignorance again. Is this something sure to pass or might it fail it and require more changes ?
Maybe it's just something you have already tested in house but need a third party testing for certification, so it's just kind of paperwork.
Or maybe it's something that may require some shielding or any changes if the finished prototype does not pass the test ?
There are rules you have to follow during development to improve the chance it will pass on first try.
Of course, there can ALWAYS be something that radiates too much, and that needs to be fixed.
But if you are carefuly during development, you can really minimize the risk.
Why on crowdsupply ? I thought ED had already managed the financing.
I mean crowd supply is fine with me, and they offer cool products (did you see the
TALOS workstation
with both computing power and blobless?) specially for the USA, but ED has already a shop and seems to manage things, doesn't him ?
Why would we need crowdsupply for the Pyra ?
The first 1000 units are funded, yes.
Once all have been shipped, we will have around 50k EUR left on our bank account - which is not enough to start the next production run on our own.
To produce 1000 more units, at least 380k EUR is needed. So yes, we either need a business angel who would like to provide us with that payment so we can produce and sell the next batch, or we need another round of preorders.
It should be easier once we delivered the first 1000 units, as then the device will already exist, but some popularity by using some crowdfunding platform should be helpful as well
