EEVblog #334 - History of PDA Teardowns

[EEVblog]

Dave.

[cloudscapes]

Could the ADC on the ninties PDA be for the resistive touch LCD? 1 meg sample/s is overkill for that obviously, but I can't imagine what else it could be for.

[oPossum]

The black marks on the PCB are resistors - probably pullup resistors because the value is not critical.

Many 68xx parts require a quadrature clock, so the xtal is 4x the clock freq to make generating the quadrature clock easy. It probably is running at 921.6 kHz. Most of the older 68xx series parts where 2 MHz max for the B suffix parts.

[Ed.Kloonk]

Giving it a thumbs up! 

[nitro2k01]

The black marks on the PCB are resistors - probably pullup resistors because the value is not critical.

I was thinking the same, but I have my doubts. I have seen this done inside a Super Nintendo controller, which made sense since it was already using carbon (I guess it is?) for the button pads. However in this case I there are two reasons why I doubt the are pullup resistors.
1) If the board isn't using the carbon coating for anything else, is/wasn't it expensive to introduce a new process, compared to placing resistors with a pick and place machine?
2) With that short distance and thickness, it seems like the resistance would be too low for a typical pull resistor.
(If it's a pull resistor, it's a pulldown and not up btw. You can see at 13:20 how they're connected to the same trace that the crystal capacitors are connected to as well, most likely gnd.)

[TradieTrev]

Good stuff Dave! I really appreciated the last HP ipaq number.

Fond memories around '05 with fellow electricians purchasing second hand ipaq's for the purpose of gps. At the time gps navigators had highly inflated prices. The cheapest alternative was to purchase a cheap pda with gps and load cracked navigation software from some random torrent site! Worked a treat for several years!

Still consider today my very first purchase of a smart phone the hp ipaq hw6965; It was really the pinnacle to the smart phone evolution. So many technologies rolled into one.

With the ever evolution of smart phones & system on a chips solutions it's expect smart phones to comprise of a chip, board, battery & touch screen! I couldn't imagine your average electronics guru building one in the back shed 

[SteveyG]

Don't know what Dave's on about regarding the HD44780 LCD driver in this video. Every LCD I come across with a HD44780 compatible interface has at least two chips on it. 

The iPaq had a Ni-MH rechargeable battery in it rather than a primary cell for keeping the contents of the SRAM. If you didn't charge the iPaq for a week, it'd lose all of your installed applications!

[freddyk]

The black lines does seem to be printed resistors. I opened up my two remaining Psion devices (models XP and LZ64) and found one with the black marks and one with regular SMT resistors.
The printed ones at the top in the first image measured between 120k - 160k.





/Fredrik

[EEVblog]

I didn't take a good look at mine. They looked for all the world like visual NP marks, so I just moved on.
It just didn't make sense to do the extra carbon step when they could have just placed the resistors.

I'll have to measure mine to confirm, but it does seem they are.

Dave.

[IanB]

Fascinating how BIG the iPAQ is! All that circuitry and board area for the wi-fi, the GPS and then the main board as well.

It would be really interesting to compare that with, say, an iPhone 4, where the wi-fi, the GPS, the 3G, the GSM, the main CPU and more besides all fits into about 3 sq in of board area. How did it get shrunk down so much?

[SeanB]

Screen printing the resistors probably saved a lot of time on the pick and place machine, or they had a limited set of part carriers and needed to run the board through in a single pass. A single silk screen mask saves a hundred picks.

[T4P]

Fascinating how BIG the iPAQ is! All that circuitry and board area for the wi-fi, the GPS and then the main board as well.

It would be really interesting to compare that with, say, an iPhone 4, where the wi-fi, the GPS, the 3G, the GSM, the main CPU and more besides all fits into about 3 sq in of board area. How did it get shrunk down so much?

Due to consumers ... engineers get clever along with very very high density ASIC's the size of your thumb and flash densities so deep if you were to emulate it with through hole parts, you would need the entire earth

[Eliminateur]

Dave,
SiRF is a very popular chipset nowadays for GPS, the latest gen the sirfstar 5 is a monster SoC, can track gps(a-gps, beacon), gnss, galileo, compass, integrates MEMS etc
the one normally used the III is pretty capable, tracks 20 sats at once(i think the standard is usually up to 12).

btw: "motoloa" must be the new Hawaian CPU manufacturer

[firewalker]

This is really bad. Once I had to repair several portable printers with such a design. When a page was being print the movement of the heads was transmitted to the crystal and it was sorting some pins on the processor, "freezing" the printing process.




Alexander.

[Eliminateur]

Also, i'm amazed at how much logic was needed for a lousy mobile 802.11b wifi module!

there's 4 TXCs alone!, that huge processor, the baseband, several front-ends/amps, horrible!
nowadays you get 802.11b/g/n (and probably more than 1 antenna) all in a single chip or at most 2 chips, the baseband the the processor

[Bored@Work]

Also, i'm amazed at how much logic was needed for a lousy mobile 802.11b wifi module!

Try to do it with a bag of transistors ...

[SeanB]

Firewalker, that crystal is glued down to the board though.

[firewalker]

Firewalker, that crystal is glued down to the board though.

Yes, I know. The ones in the printers was glued too. For a while at least.

Alexander.

[sonicj]

I'm still using a old Palm Vx to monitor various parameters on my electric golf cart. Amps, Volts, Watthours, Temp, etc. All values can be logged to the device for graphing or analysis or whatever. RS-232 straight out of the motor controller and into the Palm. Purdy handy!

Software including source can be downloaded here: AXEmon by Steve Sawtelle

[T4P]

Also, i'm amazed at how much logic was needed for a lousy mobile 802.11b wifi module!

there's 4 TXCs alone!, that huge processor, the baseband, several front-ends/amps, horrible!
nowadays you get 802.11b/g/n (and probably more than 1 antenna) all in a single chip or at most 2 chips, the baseband the the processor

Well for one nobody though of integration yet, there wasn't any need to highly integrate everything together

[Eliminateur]

Also, it surprised me seeing an Atmel IC on it, i never knew Atmel had something to do with wifi at some point(they bailed quickly it seems)

[swabaxter]

Dave,

The iPAQ line was originally made by COMPAQ and was rebranded HP after they bought the company.
You said in the video iPAQ was a Palm line - maybe a slip of the tongue.
My first PDA was a Psion II followed by a couple of Psion 3s. Then I switched to Palm M500
and also had a Dell running Windows CE at the same time.

Regards,
Stephen

[bigfun]

that spider you found in that one PDA was actually just a shed skin from a spider.  if you'd put it under a microscope you would have seen it was like an eight-legged trousers.