On 09/10/2014 06:31 PM, edward.ming.lee@gmail.com wrote:> On Wednesday, September 10, 2014 2:17:46 PM UTC-7, embdev-design wrote: >> 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. > > But who's the master and who goes first? You don't necessary want to be the 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 between your app, os and low-level driver. Configurations might depends on what app you are running. Working around Android might not be easy. Your work around could easily overwhelm whatever you gain from using the stock COTS Android. >There is an example of an RS485 converter on page 28 of the data sheet. http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf I have no idea if this is any good or answers your question. I haven't ever used RS-485
Very low-cost Android-based touch panel for HMI
Started by ●September 6, 2014
Reply by ●September 10, 20142014-09-10
Reply by ●September 11, 20142014-09-11
Dave Nadler <drn@nadler.com> wrote:> The FT232R is missing from the product list on the FTDI web page.<http://www.ftdichip.com/Products/ICs/FT232R.htm> -a
Reply by ●September 11, 20142014-09-11
On Wednesday, September 10, 2014 7:50:44 PM UTC-4, Dennis wrote:> http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdfThanks 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