P2 Evaluation Board
Dave Hein
Posts: 6,347
in Propeller 2
I am wondering when a P2 evaluation board will be available for developers to test with. This question has been asked by two other people, but I haven't seen a response to it. Personally, I'm looking forward to trying out the P2, and run my validation tests on it. I also have several programs that I've run on the P1 that I like to try on the P2, and I have some P2-specific programs that I've written. Many people have posted that they have applications that they would like to run on the P2.
The more people that test the P2, the greater the chances of catching potential issues that it may have. It seems like Peter's P2D2 would serve the purpose of evaluating the P2. Does Parallax have an estimate of when the populated boards will be available?
The more people that test the P2, the greater the chances of catching potential issues that it may have. It seems like Peter's P2D2 would serve the purpose of evaluating the P2. Does Parallax have an estimate of when the populated boards will be available?
Comments
The P2D2 is a good, compact, modest power, P2 test vehicle. I think all hand-packaged P2s (that survived) are now on P2D2 boards & Parallax ran a P&P on the P2D2F rev, so they could readily run more of those, when the full package parts arrive, if they decide to.]
Maybe Chip can send you one if they have any spares ?
Peter was also doing a motherboard carrier for P2D2.
Chip has also mentioned Parallax will do a more fully featured P2 board, but details are scant thus far.
Meanwhile, we are designing a very robust board for testing the P2 on. It has variable 3A switch-mode power supplies, as well as selectable 3.3 volt quiet regulators for each set of 8 I/O pins. It has a huge heat spreader on the bottom. This board will let us really determine the limits of the chip. I think this layout is probably a week from being done, hopefully less. We will need this board to do a lot of the data sheet work. We will make this available as a standard product. I will post images when we have something to show.
Happy to wait for the Parallax board. Right now, demands on my time are high enough that I do not make sense as a very early tester.
Sounds quite comprehensive, and good for data sheet work - but a regulator for every 8io's might spook some potential customers, who could think that level of regulator-sea is required to use P2 ?
What variable regulators have you selected ?
What is your Vin range target ?
Maybe a Reset button,SD & flash,leds,switches/buttons VGA and RCA connectors like P123
Or... maybe that's one of the first add-on boards.
There are a lot of analog apps that we haven't thought of yet, so it is impossible to put everything useful onto one board. We don't know what we don't know.
This board is not meant to be anything like the final dev pcb though, just to get something in the meantime and help me think about what might be useful.
@Bump - inserting images results in multiple copies of the link being inserted. I always have to clean it up back to one.
There are lots of pmod boards already out there. The pmod boards have male 2x6 (8gpio) or 1x6 (4gpio) headers on them
Several of our FPGA boards have pmod headers on them
I'm good with that. Nice thing is we can just make 'em and share. Count me in.
It seems there are a lot of pinout variations on those Digilent boards.
I just want to do something like this:
Pins
1 2
3 4
5 6
7 8
9 10
11 12
1 and 2 = GND
3..10 = P0..P7
11 = VIO
12 = 5V (USB)
Looks good, Peter.
We figured on putting an extra micro USB jack on the base board for high-current 5V. Those DP/DM pins can route to P56/P57.
For each 8 pins.
Are those i2c programmable, or resistor-set variable ?
Given the wide Power/operating P2 range, I've been looking into i2c regulators.
They will be settable with a screwdriver pot.
Looking forward to it.
That would be convenient in certain cases...
Chip has said in the past that they're tuned just for 3.3 volt only.
Ignoring analogue, digital inputs should be fine but output drive strengths will be reduced at 1.8 volts. They may still be useable. I have no experience myself.
Expect big slew times that may require reduced bit rates and longer handshakes.
EDIT: That was said some months back. Today I note Chip has already been experimenting with lower VIO on the real silicon - https://forums.parallax.com/discussion/comment/1448241/#Comment_1448241 And that is using analogue too!
Hmm..
Before you finalize the Board design, I'd suggest you talk to the OnSemi product manager for Regulators & Digital Potentiometers (POTs)
There is obvious appeal to using OnSemi PSU parts, but their lineup is a confusing mish-mash of old part codes, old part codes in new package, and multiple part codes and poorly documented parts... (sigh) - you want to avoid dead-end parts, & choose a good spec, long life product.
Examples :
I find a CAT5140ZI-50-GT3, digital POT & EEPROM, good price in 50k, but more in 100k, and no i2c address pin ?
Not much sign of life in the whole OnSemi POT series... Microchip do have dual-NV-pots that could adjust 1v8, 3v3 rails.
- a digital pot is one means to allow run-time control of Vcc/MHz envelope & works with any ADJ Linear and SMPS regulators.
The other approach, is to use an i2c SMPS regulator.
They do have i2c SMPS parts, in quite good prices, tho in BGA packages, and show one package variant (NCV6356) in a nicer DFN14 3.0 x 4.0 mm, but only in a 2x price Automotive qualifier. There is a non-automotive part code NCP6356 visible on the net, but suggests not the same package ?!
Usually, you can design in the higher price and switch to the other in production, less clear here if that is possible ? (aarrgh!)
In non i2c parts, they have something like NCP3170A/B OnSemi 4.5~18V 3A PGood 2500 $0.3333, but only in non-thermal SO8, & that needs compensation parts. So it comes in 'best' ranking somewhat behind the
AOZ2261QI-15 8A 2.7V~ 28V, 22-QFN (4x4) 26 mΩ / 12 mΩ typ at 12V Digikey stk 1448 49c/3k
OnSemi mention factory settings, so they may have just the right parts a right-part-code away ?
Digital pots would be complicated, wouldn't they? I need something that I can just turn with a screwdriver and check on a digital multimeter.
Yes, digital is slightly more to set up.
The CAT5140ZI-50-GT3 comes in a MSOP8, so you can easily layout for both manual & digital.
One fish-hook, is the 5140 has no address pin, but I think reverse SCL/SDA trick can work ok on 2 parts.
The appeal here, is the P2 can then adjust its own Vcc's, to suit what MHz it is expecting to use.
But if you adjust too far downward, or get the supplies into too great a disparity, the P2 will not be able to communicate, anymore, and all will be lost.
The i2c SMPS parts have defined limits, and an i2c Pot can set the limits on the 'H' wiring. (3 resistors + pot) - same as your trim pot will be (hopefully) legal (safe) at both ends.
Disparity is trickier, and the user would have to know what 'too great' was there.
That suggests there is a Vcore/Vio polygon for valid SOA - do you know what the corners of that polygon are yet ?
If that's a big issue, in the analog domain, some modest crosstalk could be deliberately added, with cross coupling components.
that means MAX Vio setting pulls up MIN Vcore, but MIN-MIN is allowed.
You set the midrange resistor value such that, if the P2 hard outputs 0v or 3v3, the maximum tug still keeps the regulator output as per the datasheet range, eg 1.65 to 2.0 volts. Hardcore types can reduce that resistor for more range if they really like
Normally this approach can introduce a bit of noise at the feedback node, but in P2's case you can output with a stiff analog 75 ohm DAC. Possibly even dither. It would work a treat and costs a pin and a resistor, provided you have a voltage dividing regulator arrangement.
Chip has indicated ~1.1V is a min and 2.0 is the MAX spec, for the core.