Very low-cost Android-based touch panel for HMI

@Lasse

Please post which store you have found this tablet.

By store you mean something local to you home country, with out shipping ?

Correct ?

Reply to
hamilton
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Yes, but those kind of functionalities can be implemented in software (directly in the app). I need only the reception and sending of bytes: it will be the app that accumulates bytes in a reception FIFO, detects a complete message, parses it and answers to it.

Reply to
pozzugno

With any two wire half duplex RS485 connections, the data direction control timing is very critical and should be implemented in hardware. Trying to implement in software, especially high data rates can fail quite badly.

Turning off the transmitter e.g. when the last byte of the message has been loaded into the shift register but not yet shifted out and the receiver will receive the last (MSB bits as ""1"). For instance the

14550 style UARTs can generate an interrupt when the last byte is loaded into the shift register, but _not_ when the byte has been completely shifted out, so you have to poll the Tx busy bit in a tight loop or read back the transmitted byte on the Rx pin.

Keeping your transmitter long after the last bit has actually been transmitted out and the other partner may already have started to send the response and there is a collision.

Reply to
upsidedown

Il 08/09/2014 09:15, snipped-for-privacy@downunder.com ha scritto:

Yes, you're right. So I need an Android OS with a RS485 driver... I don't know if it's difficult.

Reply to
pozzugno

pozz wrote in news:luf79c$5l8$ snipped-for-privacy@dont-email.me:

If you can stand a mono eInk display, look at ebook readers. A very popular one for repurposing is the Kobo Touch. It has multiple logic level serial ports accessible on its board, runs Linux and writing GUI apps for a jailbroken Kobo is a well-trodden path.

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Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED)  
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Reply to
Ian Malcolm

.@gmail.com:

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 AllW inner SoC, and maybe a wifi chip and battery. Beware of the batteries, the y may not be high quality - you could disconnect them if not needed. I'm a ssuming you'd want it rooted, so check there is root available.

SoC still need two external SDRAM and external flash loading SD. I am thin king of a single chip micro with 2M flash and 512K sram, with no external c hips.

B ram, 4GB flash for 50$

?

yes it is a local and postorder hardware store,

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but if they can sell it for ~52$ including our 25% VAT, I can't imagine buy ing a case of them from china cost much

just look at dealextreme

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-Lasse

Reply to
langwadt

l.com:

g out of China. AllWinner stuff is 'less bad' than some of the other cheap o 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 Al lWinner SoC, and maybe a wifi chip and battery. Beware of the batteries, t hey 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.

SoC still need two external SDRAM and external flash loading SD. I am thi nking of a single chip micro with 2M flash and 512K sram, with no external chips.

B ram, 4GB flash for 50$

yourself I'd think $50 is hard to meet, even with a single chip micro

yes, but for anything "android fancy" 2M flash and 512K sram isn't nearly enough, even in a lowly 256 colors the frame buffer alone will take up 80% of the ram

-Lasse

Reply to
langwadt

ing out of China. AllWinner stuff is 'less bad' than some of the other che apo SoCs as far as software openness goes - that means there's a little mor e 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.

er SoC still need two external SDRAM and external flash loading SD. I am t hinking of a single chip micro with 2M flash and 512K sram, with no externa l chips.

2MB ram, 4GB flash for 50$

ch yourself I'd think $50 is hard to meet, even with a single chip micro

enough, even in a lowly 256 colors the frame buffer alone will take up 80% of the ram

You can get custom LCD controller with

Reply to
edward.ming.lee

oming out of China. AllWinner stuff is 'less bad' than some of the other c heapo SoCs as far as software openness goes - that means there's a little m ore of an ecosystem about it. Such a tablet is basically a touchscreen, th e AllWinner SoC, and maybe a wifi chip and battery. Beware of the batterie s, 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.

nner 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 exter nal chips.

512MB ram, 4GB flash for 50$

ouch yourself I'd think $50 is hard to meet, even with a single chip micro

ly enough, even in a lowly 256 colors the frame buffer alone will take up 8

0% of the ram

(my laptop keeps acting on it's own mind.)

You can get custom LCD controller with frame buffers. You can even impleme nt drawing primitives in the LCD controller, or even a Java VM. For 10k pc s, things are possible.

Reply to
edward.ming.lee

Den mandag den 8. september 2014 16.48.09 UTC+2 skrev snipped-for-privacy@gmail.com:

:

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 batter ies, 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.

winner 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 ext ernal chips.

, 512MB ram, 4GB flash for 50$

touch yourself I'd think $50 is hard to meet, even with a single chip micr o

arly enough, even in a lowly 256 colors the frame buffer alone will take up 80% of the ram

ment

,

sure anything is possible. I use an LCD controller with frame buffer, but; having to implement a whole new framework to use the primitives instead of an existing portable one that paints directly to a frame bufferis a pain in the rear, an IC with +1MB sram isn't free, and the interface is slow compa red to a frame buffer in internal ram.

and you can't fit much fancy graphics in a 2MB flash

-Lasse

Reply to
langwadt

m:

te:

ts coming out of China. AllWinner stuff is 'less bad' than some of the oth er cheapo SoCs as far as software openness goes - that means there's a litt le 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 batt eries, they may not be high quality - you could disconnect them if not need ed. I'm assuming you'd want it rooted, so check there is root available.

llwinner 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 e xternal chips.

er, 512MB ram, 4GB flash for 50$

ve touch yourself I'd think $50 is hard to meet, even with a single chip mi cro

nearly enough, even in a lowly 256 colors the frame buffer alone will take up 80% of the ram

t drawing primitives in the LCD controller, or even a Java VM. For 10k pcs , things are possible.

; having to implement a whole new framework to use the primitives instead o f an existing portable one that paints directly to a frame buffer is a pain in the rear, an IC with +1MB sram isn't free, and the interface is slow co mpared to a frame buffer in internal ram.

I don't think the OP is interested in fancy graphics and/or video. It woul d be too slow on serial RS485 anyway. He is probably thinking about button s, dropdown list, etc. If you limit the output to reasonable colors (e.g.

64), you can build the frame buffer with 128K sram. 64K sram LCD controlle rs are very common. 128K might be slightly more expensive, but much cheape r than external SDRAM.

SDRAM might not be too bad by itself. But the supporting circuit and CPU r equirements drive up components and assembly costs.

Reply to
edward.ming.lee

com:

rote:

lets coming out of China. AllWinner stuff is 'less bad' than some of the o ther cheapo SoCs as far as software openness goes - that means there's a li ttle more of an ecosystem about it. Such a tablet is basically a touchscre en, the AllWinner SoC, and maybe a wifi chip and battery. Beware of the ba tteries, they may not be high quality - you could disconnect them if not ne eded. I'm assuming you'd want it rooted, so check there is root available.

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.

nner, 512MB ram, 4GB flash for 50$

tive touch yourself I'd think $50 is hard to meet, even with a single chip micro

.

t nearly enough, even in a lowly 256 colors the frame buffer alone will tak e up 80% of the ram

ent drawing primitives in the LCD controller, or even a Java VM. For 10k p cs, things are possible.

ut; having to implement a whole new framework to use the primitives instead of an existing portable one that paints directly to a frame buffer is a pa in in the rear, an IC with +1MB sram isn't free, and the interface is slow compared to a frame buffer in internal ram.

uld be too slow on serial RS485 anyway. He is probably thinking about butt ons, dropdown list, etc. If you limit the output to reasonable colors (e.g . 64), you can build the frame buffer with 128K sram. 64K sram LCD control lers are very common. 128K might be slightly more expensive, but much chea per than external SDRAM.

just because data is slow doesn't mean you can't use a lot of graphics to display it

that low number of bits a limited resolution will have nothing like the look or feel of an android tablet

-Lasse

Reply to
langwadt

ablets 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 touchsc reen, 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 availabl e.

he Allwinner SoC still need two external SDRAM and external flash loading S D. I am thinking of a single chip micro with 2M flash and 512K sram, with no external chips.

winner, 512MB ram, 4GB flash for 50$

citive touch yourself I'd think $50 is hard to meet, even with a single chi p micro

il.

n't nearly enough, even in a lowly 256 colors the frame buffer alone will t ake up 80% of the ram

ement drawing primitives in the LCD controller, or even a Java VM. For 10k pcs, things are possible.

but; having to implement a whole new framework to use the primitives inste ad of an existing portable one that paints directly to a frame buffer is a pain in the rear, an IC with +1MB sram isn't free, and the interface is slo w compared to a frame buffer in internal ram.

would be too slow on serial RS485 anyway. He is probably thinking about bu ttons, dropdown list, etc. If you limit the output to reasonable colors (e .g. 64), you can build the frame buffer with 128K sram. 64K sram LCD contr ollers are very common. 128K might be slightly more expensive, but much ch eaper than external SDRAM.

display it

ook or feel of an android tablet

You can get the look and feel without the background. Other than the backg round picture, Android only use a very small subset of colors. Except for loading custom picture buttons, you can't really assign arbitrary color sch emes without very extensive custom modifications. Most apps only use the c ustom library of a few colors. Regarding colorful backgrounds, sometimes I turns them off because they are too distracting anyway. That's true for b oth my Android phones and laptops.

Of course, there is no absolute right or wrong. We are just offering two o pposite opinions for the OP to pick and choose.

Reply to
edward.ming.lee

Have a look at eg. Qt.

-a

Reply to
Anders.Montonen

Hi pozz,

Even a micro with no build in LCD controller will do the job if you do not need animation or other moving objects, and the system can be a industrial grade design. Not sure about the enclosure requirements, but a single board design can be achieved. We did a similar application with nice graphic and touch feedback, but in lower quantities.

gabriel

Android OS. I'll use only the LCD, the touch panel and a serial interface (RS485). A USB device port (to make a connection with a PC) and/or USB host port (for connecting USB pen drives) would be nice. The size of LCD could be from 5 to 7".

other

everything that need Android/Linux/networking.

interactions (like on Android smartphones).

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.

pcs.

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Reply to
embdev-design

I just bought a "Landfill Ready" low end Android for $43.04 at the local Staples. The link is here

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It comes with an OTG cable so that the USB port can be used in host mode.

FDTI now provides Android drivers for their chips, see

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As a proof of concept exercise I downloaded the FDTI serial terminal app from the Google store.This uses the Android driver mentioned above. I then attached a FDTI TTL-232R-3.3 cable between the Android and my Beaglebone Black serial console header. Fired up the FDTI serial terminal on the Android and reset the Beaglebone and got the Beaglebone startup display on my new Android.

FDTI also makes an rs485 cable.

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At unit prices it is a bit above your $50, but in quantity I suspect it would be in your range - maybe do your own adapter using the FDTI chip to get exactly the features you need.

Since this would use generic support you would be less dependent on a particular Android model/supplier.

Reply to
Dennis

The FTDI datasheet says this cable uses FT232R, and says: "The FT232R datasheet, DS_FT232R, is available at

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"

The link in the datasheet is broken. The FT232R is missing from the product list on the FTDI web page.

Does this product exist? I was wondering if it was usable for RS-485 multi-drop; in particular, how does it handle direction-switching, addressing, and speed requirements...

Anybody know if this is a viable solution?

Thanks, Best Regards, Dave

Reply to
Dave Nadler

A typical RS232 to RS485 interface will switch the direction based on the slave side traffic, by default being listening to the master (tablet). It will switch back after a short delay (equivalent of 3 characters) after the slave ends the transmission. The speed affects only the 3 characters delay timer.

Gabriel

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Reply to
embdev-design

slave side traffic, by default being listening to the master (tablet). It will switch back after a short delay (equivalent of 3 characters) after the slave ends the transmission. The speed affects only the 3 characters delay timer.

But who's the master and who goes first? You don't necessary want to be th e master just because you have a screen. You could be attaching as a slave or just a monitor station. There are lots of settings and interaction bet ween your app, os and low-level driver. Configurations might depends on wh at app you are running. Working around Android might not be easy. Your wo rk around could easily overwhelm whatever you gain from using the stock COT S Android.

Reply to
edward.ming.lee

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No idea I have never done RS-485

Reply to
Dennis

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