Very low-cost Android-based touch panel for HMI

pozz · 2014-09-06T14:55:40+00:00

I need a very low-cost (50USD for quantity) touch panel running 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". I don't need SD, Ethernet, WiFi, CAN, RTC, battery, Bluetooth and other nice things. Just a serial interface. And I don't need many features of Android, such as addressbook, phone calls and messages management, TCP/IP and Internet connections, app installation flexibility and similar things. The final application will be a HMI with good graphics and human interactions (like on Android smartphones). I know I can use a powerful CPU core module (generally with a SODIMM interface) and design a custom mainboard, but I think the final price of the widget will be higher than my target low price. I'm ready to design my custom board with MPU and memories, but I need to start at least from a reference design with schematics and software (Android) running well. I don't have the knowledge to hack the Android/Linux kernel. Any suggestions on a off-the-shelf product or a open hardware design to start from?

Sep 06, 2014 42 Replies

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Dennis 11 years ago

There is an example of an RS485 converter on page 28 of the data sheet.

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I have no idea if this is any good or answers your question. I haven't ever used RS-485

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Anders.Montonen 11 years ago

-a

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Dave Nadler 11 years ago

Thanks Dennis, I gave up as its not listed on FTDI's summary product page...

Anyway, the FT232R datasheet says it can only do 7 or 8 data bits. If that's so, this part will not work for lots of RS-485 networks that use 9-bit addressing...

IIRC Exar has parts that do this (but no Android drivers).

OP was not specific in his RS-485 requirement! He might be best off building a small dongle that does USB to the host with vanilla CDC, with the dongle implementing the specific RS-485 protocol as he requires. This would allow easier integration with hosts not able to meet timing requirements etc; I've done similar...

Hope that helps, Best Regards, Dave

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