Re: LCD evaluation and other preparations for FC handset
OK, so I picked up the package from HaoRan LCD company and examined their LCDs. Two observations, one expected, the other unexpected: The expected observation: the end of the FPC tail that is meant to go into a connector has straight edges, the corners are sharp 90 deg, no rounding. The unexpected observation: the contacts are on the "wrong" side. On both the historical GPM526A0 LCD in the Pirelli DP-L10 and the shiny new KD020C-2A from Startek the contacts appear to be on the top when the FPC tail is stretched out or on the bottom when the FPC tail is folded under the LCD; HaoRan's HT020K1QC36S has them on the opposite side. Looking at their datasheet more carefully I see that the drawing included therein does indicate the contact location, i.e., the delivered product does match the datasheet description - I simply overlooked it when I originally studied this DS, as I had naively assumed that the contacts would be in the "natural" location. Having the contacts on the wrong side fully invalidates my earlier idea of using a Hirose FH33 series connector - these connectors are not made in a "contacts on top" version, and it is difficult to fault Hirose for not making such connectors as the "contacts on top" arrangement is highly unnatural. In light of this discovery I have revised my plan of action: given that our current most immediate need is to compare the LCD picture quality between HaoRan and Startek and help guide the decision between these two vendors, in the interest of time expediency I am simplifying my HT020K1QC36S LCD test board idea: I will put this LCD on the test board with its tail stretched out (not folded under like it would need to be in the real handset), and use the known-good FH12-36S-0.5SH connector. This test board won't help with prototyping the mechanical arrangement for the handset, but it will hopefully allow us to solidify the Startek vs. HaoRan decision. Given that the two vendors' LCDs have their FPC contacts on relatively opposite sides, the mechanical arrangement would have to be quite different for one vs. the other, thus it would be easier to select the LCD vendor first based on the picture quality comparison, and then work out the mechanical arrangements for that chosen LCD. Now that I have the FPC connector picked out for the HaoRan LCD test board and the discussion with Hirose is being postponed until after the LCD picture quality comparison, there is no more obstacle and I can now proceed with the design of this very simple test PCB. I am hoping to get this PCB design done and sent out to fab some time this week. Hasta la Victoria, Siempre, Mychaela aka The Mother ___ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community
Re: LCD evaluation and other preparations for FC handset
> [...] this idea will NOT work for our FreeCalypso handset. Our PCB will > have 8 layers with lots of traces on every layer (intricate 2+4+2 HDI > structure with inner buried vias and two levels of staggered microvias > on each side), and the width of the PCB will extend only slightly past > the width of the LCD module. If we had to cut a slot the width of the > LCD's FPC tail in the middle of our PCB, it would cut through all of > our layers and present an obstacle for signal routing, completely > crippling our PCB layout. In short, just no - totally not suitable > for a PCB of our complexity. Then, another idea is rotating the LCD 180 degrees, then using some kind of LCD command that would allow to rotate the image accordingly - or rewrite the framebuffer output routines accordingly. I assume that, if you're not going through the center of the PCB, but making a slot on the top, the PCB routing shouldn't be as much of a pain. I understand that you've already picked this path, but I do think it's necessary to point out other options, since I know it might not be as obvious =) Cheers! Arsenijs ___ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community
Re: LCD evaluation and other preparations for FC handset
Hi Mychaela, > * For the data and control lines, the other end of the wire would need > to go to a pin on an FT2232D breakout board just like the ones we use > for FCDEV3B UARTs - how would this connection be made? Each Kynar wire would be soldered to a classic 2.54mm female wire that can be plugged into the FT2232D, with the exception of bus pins you mention. > * Several pins on the LCD need to be connected to GND, and several LCD > pins need to be connected to the 3.3V power rail. There are two GND > pins and one 3.3V pin on the FT2232D breakout board. How would these > "bus bar" connections be accomplished? Simply by soldering the Kynar wires together, and then to a single 2.54mm wire to GND or 3.3V. > cathodes are brought out separately, and each needs its own series > resistor - a 120 ohm resistor between each LEDK pin and GND. Where > would these resistors go in your proposal? Well series resistors can be added to each Kynar wire, and then soldered to a single 2.54mm wire that will be connected to ground. > But if you think you can solve all of the above, I would GLADLY send > you one of these HaoRan LCD sample pieces plus an extra FT2232D board > (identical to the one I assume you already have for FCDEV3B UARTs) if > you can then send me back an assembled and working arrangement. Heck, > I could even send you two LCD pieces (the sales lady from HaoRan sent > me 5) so you could keep another fully assembled setup for yourself. :) > All of the software needed to make it work resides in the > freecalypso-hwlab Hg repository on Bitbucket. That's very doable, although I'd like to know the spacing between each pad on the flex connector. If the spacing is too small (like < 0.2mm) then I'm not sure I'm up to the task. --DS ___ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community
Re: LCD evaluation and other preparations for FC handset
Hi Arsenijs! > A common practice is also putting the connector on the other side of > the PCB, then making a slot which the cable is supposed to go through. > This way, you don't have to worry about LCD and the connector > occupying the same space. Startek folks (one of the two LCD vendors I am working with) suggested the same idea to me. I suppose this idea might work if there is a great scarcity of electronics on the board: if the entire logic of the phone is in one chip (no wide external memory buses, no chipset internal interconnections) and the LCD is used in the SPI interface mode, connected to the all-in-one chip with just a few wires, then there would be plenty of room on the back side of the board, and the slot can probably be made in the middle of the PCB without totally crippling the signal routing ability. I suppose this idea could work for those 100% closed and proprietary "modern" dumbphones based on MTK or Spreadtrum chips. But this idea will NOT work for our FreeCalypso handset. Our PCB will have 8 layers with lots of traces on every layer (intricate 2+4+2 HDI structure with inner buried vias and two levels of staggered microvias on each side), and the width of the PCB will extend only slightly past the width of the LCD module. If we had to cut a slot the width of the LCD's FPC tail in the middle of our PCB, it would cut through all of our layers and present an obstacle for signal routing, completely crippling our PCB layout. In short, just no - totally not suitable for a PCB of our complexity. I already know what I want, and I will not settle for anything less: I want an LCD whose FPC tail is meant to be soldered rather than connectorized. Both Startek and HaoRan said they can make such, but with an MOQ of 1000 pcs, which would be about $3200 at HaoRan's prices or about $5600 at Startek's prices. It is more than I can afford right now, so for the first prototype I will have to use a dirty hack (lift the existing connectorized LCD above the PCB with double-sticky tape to make room for the connector), but at a much later stage of the project (after the first prototype has been built and the software has been brought into shape) I will probably have to just bite the bullet and pay the 1000 pcs price to get the LCDs I really want. For the first prototype I am thinking of my particular hack with the double-sticky tape to lift the LCD as opposed to some other dirty hack in order to make our PCB design as close as possible to what I ultimately desire with a solder-down LCD: this way when we do get the good LCDs, the layout change will be absolutely minimal. But meanwhile I need to build some kind of test rig for HaoRan's LCD (it's a one-off hack, so it doesn't matter how hacky or dirty or ugly it is) so I can visually compare the picture quality between HaoRan and Startek LCDs. I seek an LCD of the very highest picture quality, hence the decision between HaoRan and Startek will need to be based on whichever LCD produces the best picture quality. I already know from having tested it that Startek's LCD is very good, but I have yet to see HaoRan's. Thus I need a test rig for HaoRan's LCD so I can do the comparison. I expect to be picking up these HaoRan LCDs from the mailbox service later today, and then I will need to start the dialogue with Hirose (the FPC connector manufacturer) about the straight vs. tapered FPC end strangeness. If Hirose folks say that a straight FPC end cannot be reliably inserted into an FH33 series connector and that it is some kind of inexplicable accident that Foxconn somehow got it to work in the Pirelli DP-L10, then I'll just use the taller FH12 series connector for the HaoRan LCD evaluation board - but if there is some way to use FH33, I would like to use that as it would be very helpful for the handset prototype: it's bad enough already that we'll have to use double-sticky tape to lift the LCD, and having to use an even taller connector than the one in the Pirelli phone would be even worse. M~ ___ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community
Re: LCD evaluation and other preparations for FC handset
> At first I thought "OK, fine, I'll just put the needed FPC connector > on our board", but then I realized that there is a problem: where will > the body of the connector go? Two solid objects cannot occupy the > same space at the same time... How can the LCD rest flat against the > PCB surface if there a connector sitting underneath? The thinnest FPC > connectors I could find (Hirose FH33 series) have 1.2 mm height above > the PCB, and I have a difficult time imagining how anyone can make an > FPC connector thinner than this. A common practice is also putting the connector on the other side of the PCB, then making a slot which the cable is supposed to go through. This way, you don't have to worry about LCD and the connector occupying the same space. Cheers! Arsenijs. ___ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community
