> One point I'm trying to get across :) - RS485 is a largely alien technology in the RasPi/Android sphere. Paradoxically, WiFi isn't.In Android, you deal with socket at the low level and url at the high level, just like most standard software under UNIX/Linux. And in the old days, UNIX runs with serial connections, without Wifi. As long as you have ppp, slip or something on RS485. Android/Java would not know or care about what's running under it.
Very low-cost Android-based touch panel for HMI
Started by ●September 6, 2014
Reply by ●September 7, 20142014-09-07
Reply by ●September 7, 20142014-09-07
edward.ming.lee@gmail.com wrote:> >> One point I'm trying to get across :) - RS485 is a largely alien >> technology in the RasPi/Android sphere. Paradoxically, WiFi isn't. > > In Android, you deal with socket at the low level and url at the high > level, just like most standard software under UNIX/Linux.But while they are similar, serial port connections aren't exactly the same API as for sockets. You talk about ppp/slip - to be sure. That's doable... but... There's this: http://examples.javacodegeeks.com/android/core/socket-core/android-socket-example/ Not exactly daunting, but still a parcel of work.> And in the > old days, UNIX runs with serial connections, without Wifi. > > As long as you have ppp, slip or something on RS485. Android/Java > would not know or care about what's running under it. >I've little doubt that's true, but I don't think you have to add anything to get WiFi on an Android, but you have to add an RS485 adapter and it'll be (possibly) quite a bit slower. If you can get things to agree to a 1/4 Mbit connection, then it's probably fast enough - although most likely it's still half-duplex ( and will have long turnaround times ). If I make my guess, the Wifi dongle for a RasPi will be about the same cost as two RS485 adapters. -- Les Cargill
Reply by ●September 7, 20142014-09-07
rickman <gnuarm@gmail.com> wrote:> Do you think your price target is realistic? For $50 you will be hard > pressed to find a small tablet which is about your specs minus the > RS-485 plus a few very low cost peripherals. I would think they way to > go is to find the lowest priced tablet you can and add a USB RS-485 > adapter. > > http://www.dxsoul.com/product/gonomad-p702a-7-action-7013-android-4-1-tablet-pc-w-512mb-ram-4gb-rom-black-901295052#.VAt6ixY9TAkI'd be tempted to look at the various Allwinner-based tablets coming out of China. AllWinner stuff is 'less bad' than some of the other cheapo SoCs as far as software openness goes - that means there's a little more of an ecosystem about it. Such a tablet is basically a touchscreen, the AllWinner SoC, and maybe a wifi chip and battery. Beware of the batteries, they may not be high quality - you could disconnect them if not needed. I'm assuming you'd want it rooted, so check there is root available. In theory, if the innards are the same as other Allwinner tablets you're insured a bit from supply-chain issues: the SoC is the same so pick up another cookie-cutter tablet. Contacting the factory on Alibaba might be the way to get a more consistent supply (but be prepared for language issues). But a warning: you're at the 'cheap junk' end of the market here. It may work, but what you save on ticket price you might spend instead on supply hassles. But could be worth it if the volume is high and the timescale is short (don't expect the same to be available next year). Theo
Reply by ●September 7, 20142014-09-07
Just ran across this: http://www.alibaba.com/product-detail/VESA-Mounting-Android-Tablet-Integrated-low_900890641.html It does state that it has RS485. hamilton
Reply by ●September 7, 20142014-09-07
> I'd be tempted to look at the various Allwinner-based tablets coming out of China. AllWinner stuff is 'less bad' than some of the other cheapo SoCs as far as software openness goes - that means there's a little more of an ecosystem about it. Such a tablet is basically a touchscreen, the AllWinner SoC, and maybe a wifi chip and battery. Beware of the batteries, they may not be high quality - you could disconnect them if not needed. I'm assuming you'd want it rooted, so check there is root available.It would be difficult to meet the target price of $50. The Allwinner SoC still need two external SDRAM and external flash loading SD. I am thinking of a single chip micro with 2M flash and 512K sram, with no external chips.
Reply by ●September 7, 20142014-09-07
On 9/7/2014 2:32 PM, hamilton wrote:> Just ran across this: > > http://www.alibaba.com/product-detail/VESA-Mounting-Android-Tablet-Integrated-low_900890641.html > > > It does state that it has RS485.I did a search on Alibaba and found a number of units. Not sure of all the prices but $50 sounds like it could be in the range. Only one clearly supported RS-485 and showed a module in the image, but said it was an option. Some of the others said RS-485 in the list of features/interfaces, but weren't clear about it while others only mention RS-485 in the listing title. Still, it might be worth setting up a conversation with a few of them. Certainly this is the easy route to hardware if you can be sure they will be making them long enough to suit your needs. I guess you can always find a newer, similar unit if they stop making this one. -- Rick
Reply by ●September 7, 20142014-09-07
Theo Markettos wrote:> rickman <gnuarm@gmail.com> wrote: >> Do you think your price target is realistic? For $50 you will be hard >> pressed to find a small tablet which is about your specs minus the >> RS-485 plus a few very low cost peripherals. I would think they way to >> go is to find the lowest priced tablet you can and add a USB RS-485 >> adapter. >> >> http://www.dxsoul.com/product/gonomad-p702a-7-action-7013-android-4-1-tablet-pc-w-512mb-ram-4gb-rom-black-901295052#.VAt6ixY9TAk > > I'd be tempted to look at the various Allwinner-based tablets coming out of > China. AllWinner stuff is 'less bad' than some of the other cheapo SoCs as > far as software openness goes - that means there's a little more of an > ecosystem about it.There is still usually a "blob" in the BSP parts for 'em.> Such a tablet is basically a touchscreen, the AllWinner > SoC, and maybe a wifi chip and battery. Beware of the batteries, they may > not be high quality - you could disconnect them if not needed. I'm assuming > you'd want it rooted, so check there is root available. > > In theory, if the innards are the same as other Allwinner tablets you're > insured a bit from supply-chain issues: the SoC is the same so pick up > another cookie-cutter tablet. Contacting the factory on Alibaba might be > the way to get a more consistent supply (but be prepared for language > issues). >The thing that might be important is to find the OTG port and image-off the NAND. I know the Cubie boards have quite a bit of community for them; it's not clear that this is true of the tablets. And it's anything but clear how much they'd all have in common> But a warning: you're at the 'cheap junk' end of the market here. It may > work, but what you save on ticket price you might spend instead on supply > hassles. But could be worth it if the volume is high and the timescale is > short (don't expect the same to be available next year). >You really kind of have to be your own escrow service. You can always eBay off extras.> Theo >-- Les Cargill
Reply by ●September 7, 20142014-09-07
On Saturday, September 6, 2014 10:55:40 AM UTC-4, pozz wrote:> I need a very low-cost... with serial interface (RS485).To clarify, you need a RS485 driver that supports operation on a multi-drop link, with addressed and broadcast reception, and/or master function? (as opposed to simple point-to-point)
Reply by ●September 7, 20142014-09-07
Den s�ndag den 7. september 2014 20.33.31 UTC+2 skrev edward....@gmail.com:> > I'd be tempted to look at the various Allwinner-based tablets coming out of China. AllWinner stuff is 'less bad' than some of the other cheapo SoCs as far as software openness goes - that means there's a little more of an ecosystem about it. Such a tablet is basically a touchscreen, the AllWinner SoC, and maybe a wifi chip and battery. Beware of the batteries, they may not be high quality - you could disconnect them if not needed. I'm assuming you'd want it rooted, so check there is root available. > > > > It would be difficult to meet the target price of $50. The Allwinner SoC still need two external SDRAM and external flash loading SD. I am thinking of a single chip micro with 2M flash and 512K sram, with no external chips.I can go to a store an get a 7" tablet with a dual core Allwinner, 512MB ram, 4GB flash for 50$ if you buy parts and build something with a 7" lcd and capacitive touch yourself I'd think $50 is hard to meet, even with a single chip micro -Lasse
Reply by ●September 7, 20142014-09-07
On Sunday, September 7, 2014 3:45:58 PM UTC-7, lang...@fonz.dk wrote:> Den s�ndag den 7. september 2014 20.33.31 UTC+2 skrev edward....@gmail.com: > > > > I'd be tempted to look at the various Allwinner-based tablets coming out of China. AllWinner stuff is 'less bad' than some of the other cheapo SoCs as far as software openness goes - that means there's a little more of an ecosystem about it. Such a tablet is basically a touchscreen, the AllWinner SoC, and maybe a wifi chip and battery. Beware of the batteries, they may not be high quality - you could disconnect them if not needed. I'm assuming you'd want it rooted, so check there is root available. > > > It would be difficult to meet the target price of $50. The Allwinner SoC still need two external SDRAM and external flash loading SD. I am thinking of a single chip micro with 2M flash and 512K sram, with no external chips. > > I can go to a store an get a 7" tablet with a dual core Allwinner, 512MB ram, 4GB flash for 50$Yes, economy of scale.> if you buy parts and build something with a 7" lcd and capacitive touch yourself I'd think $50 is hard to meet, even with a single chip microDoable for 10k pcs. You can get parts much cheaper than retail.