Hi,
2011/5/23 Steve Wiseman <
steve@arbury.com>:
> We do not have:
> ETK (trace)
> GPT outputs (PWM channels)
I just wanted to point out PWM channels are useful for LCD backlight
control or is there an alternative?
> Contentious:
> Not many SPIs. Do we care? Anyone use them, except for audio?
> One MMC is missing. Anyone care? We've got NAND for fast storage, and USB for I/O.
If I recall correctly SPI has its own clock line which it is useful
for keeping communications in sync while I2C was a bit more painful to
keep bytes in sync when driving multiple devices (i2c or else) from
one clock source.
> --------------Concerns: ---------------------
> Power.
> The mission for Balloon4 is to have it manufacturable, which means that TI's Power Management ICs (PMICs) are, in general, tricky. The best ones are in 0.4mm BGA packages, which is _not_ good for PCB costs. They're also notoriously fragile. Expensive. Single-sourced.
> The ones in packages we can use aren't rated to drive the OMAP at its highest speed profiles. (The OMAP counts its toes, then checks its process geometry, temperature, phase of moon, then chatters over i2c to the PMIC to pick a supply voltage that will probably allow it to work without failing unreasonably quickly. This is explicitly defined in the datasheet - we don't have to use a PMIC, we could build a little micro to listen to the i2c, and set the voltage as requested. But, if we're having a little micro, what else would we want it to do? Boot stuff? RTC in ultra-powerdown? Battery Charging? Keyboard Checking?)
If we were to use an external micro, we are already using STM32 H107
Cortex M3 micro, maybe it could be reused for such purpose. A good
PMIC is still preferred in my opinion.
> The spiffy PMICs also tend to have handy stuff like USB OTG PHYs, which can be used to boot. If we don't have the exact same phy, I'm unconvinced we'll be able to boot from USB. I don't think I care. Does anyone? We can still boot from (at least) serial, NAND, MMC...
> DRAM:
> Oh good grief. Been round this a dozen times. Anyone know what LPDDR devices actually exist? 1 or preferably 2 Gbit. (although I'll take 4GBit if they exist). Not POP package. If there's a sweet spot, I have yet to find it. Anyone with access to purchasing channels, anything that says 'LPDDR' is fair game. DDR, DDR2, DDR3 are not acceptable. 'Mobile SDR' is not acceptable. 'Mobile DDR' may be. x16 or x32 are both of interest (although x32 may or may not be acceptable to run 2 banks. The POP packages run with 2 banks of x32, but with short buses. The datasheet says not to, so, if we want a low-risk 2-chip solution, we may need x16 chips, but I'll take what we can get).
As a suggestion, have you seen:
http://www.elpida.com/en/
http://www.micron.com/products/
http://www.om-nanotech.com/mobile-lpddr.asp
> Everything else: Easy.
Do we have RTC chip? :-)
> Anyone who wants a huge pile of schematics, spreadsheets, annotated datasheets and pinmux data files, let me know.
I would not mind to review them.
Cheers,
--
Héctor Orón -.. . -... .. .- -. -.. . ...- . .-.. --- .--. . .-.
"Our Sun unleashes tremendous flares expelling hot gas into the Solar
System, which one day will disconnect us."
-- Day DVB-T stop working nicely
Video flare:
http://antwrp.gsfc.nasa.gov/apod/ap100510.html
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