[Arm-netbook] Interchangeable screen

[GaCuest]

En 21 de septiembre de 2015 en 14:17:10, Luke Kenneth Casson Leighton (lkcl at lkcl.net) escrito:
> On Mon, Sep 21, 2015 at 12:49 PM, GaCuest wrote:
> > En 21 de septiembre de 2015 en 13:27:19, Hrvoje Lasic (lasich at gmail.com) escrito:  
> >> Maybe try to focus on one model in beginning, to make yourself easier job
> >> going to market than proceed with three models. I don't know much about
> >> your target audience and why you want three models (only I like your idea*,*
> >> but my vision here is extremely limited) but believe me you will have more
> >> then enough challenges on one model and by the time you have feedback from
> >> customers you will gain some traction and have more than one good idea how
> >> to improve product. Even if you have resources to make three models, maybe
> >> you can direct this resources to make prepare some good game, to make
> >> product more likable, playable etc something that could help your project
> >> in different way...Just an thought…
> >
> > Well, we will not create three different models.
> >
> > Simply we create a base model (without display) and based on it you can add modules with  
> different displays. The problem is that not everyone will know to put the modules, so  
> we will sell configurations with mounted display modules.
> >
> > It is similar to BananaPi with different display models available. But with a case around  
> the display-CTP to screw to the case of the game handheld games console.
>  
> i just thought of something which you *really* really should
> consider *well* before doing this type of modular design for LCDs.
>  
> the cost of even a 4-layer prototype board vs a 2-layer prototype
> board is *literally* a 5 to 10x jump in price. $40 for 2 boards 1.5mm
> thick can easily become $200 to $400 for 2 4-layer boards.
>  
> as you have *three* such boards... no, five because you have main
> PCB, power PCB, and 3 LCD modules, consider trying to make the boards
> 2 layer ***BEFORE*** committing any other resources to the modular
> concept.
> 

We have 3 PCB (first for all components and second/third for controls). Then we have two PCB for 480p display and 720p display (non-display model does not have that PCB).

> as you have very short signals you should be ok but for goodness sake
> make absolutely sure that you can route all the differential pairs
> (MIPI, LVDS, whatever) on a single layer, directly from the connector,
> directly to the IC, directly to the LCD connector. make absolutely
> sure that you have room to surround and separate the differential
> pairs with GND-tied vias.
>  
> take a look at this for example:
>  
> http://hands.com/~lkcl/eoma/laptop_15in/laptop_2layer_pcb1.png
>  
> in the bottom right, you can see the LVDS connector, and above it the
> SN75LVDS83b. there appears to be some unspoken communication between
> the designers of all the parts so that the LVDS differential pairs
> line up *DIRECTLY*. i have places GND vias in between (as best i
> can), i am not happy that the LVDS signals have to divert around them,
> but the cost of boards if the vias are smaller goes up from $40 for 2
> to over $150 for 2.
>  
> then, look in the left corner. that's a GL850G 4-port USB Hub IC.
> those "GND" vias in between and surrounding the tracks go *all the
> way* up the board, it took several days to arrange because i had to
> adjust it and correct this arrangement several times. it's by no
> means perfect, but it is what it is.
>  
> you can also see top middle, 7 wires in between GND tracks, those are
> the SD/MMC lines, they're getting quite fast these days so i thought
> it best to put GND guides around them.
>  
> strictly speaking from what i gather you are supposed to actually
> isolate the GND tracks at the outer edges, not let them become part of
> a larger GND plane. also you are supposed to leave a large distance
> to any other components. also you are supposed to leave a large
> distance in between each differential pair.
> 

Our idea is to do it in 2 layers.

The only problem is that the PCMCIA connector is on the bottom layer and the FFC connector for the display goes on top layer. Anyway, put the display in another PCB and attach using FFC makes the design easier because we can put the FFC connector where we want.

Thanks for all the tips. I can not use the tips because I do not know about PCB designs but I hope the tips will be useful to Daniel.

> l.
>  
> _______________________________________________
> arm-netbook mailing list arm-netbook at lists.phcomp.co.uk
> http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
> Send large attachments to arm-netbook at files.phcomp.co.uk