Hardware flow control in am335x problem

shammi kaplesh

I am not able to control RTS line from my application. I am following the link http://e2e.ti.com/support/arm/sitara_arm/f/791/p/337173/1438706#1438706

Is hardware flow is working in am335x. i want to control rts cts line from my application.

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

The post you refer describes exactly that. Please read the entire thread.

0 shammi kaplesh over 9 years ago in reply to Biser Gatchev-XID

Expert 1475 points

I tried the sample application provided on this post.But i am not able to toggle RTS line. Software wise its changing but i checked in CRO its not getting changed.

0 Biser Gatchev-XID over 9 years ago in reply to shammi kaplesh

TI__Guru**** 393215 points

Have you pinmuxed it to the RTS mode?

0 shammi kaplesh over 9 years ago in reply to Biser Gatchev-XID

Expert 1475 points

yes. RTS as output and CTS as input line.

0 Biser Gatchev-XID over 9 years ago in reply to shammi kaplesh

TI__Guru**** 393215 points

What I mean is are RTS and CTS pinmuxed to UART mode or GPIO?

0 shammi kaplesh over 9 years ago in reply to Biser Gatchev-XID

Expert 1475 points

it is muxed for UART mode.

0 Biser Gatchev-XID over 9 years ago in reply to shammi kaplesh

TI__Guru**** 393215 points

OK, next thing is have you enabled HW flow control on the other side (PC terminal or whatever is connected to the UART)?

0 shammi kaplesh over 9 years ago in reply to Biser Gatchev-XID

Expert 1475 points

Hardware flow is enabled from both side. But from software on board side i am not able to disable RTS/CTS functionality.i Think AutoRTS autoCTS is enabled .
Actually i want to control RTS CTS line from my application.

0 Biser Gatchev-XID over 9 years ago in reply to shammi kaplesh

TI__Guru**** 393215 points

You can control the RTS line manually by toggling bit RTS in the MCR register (section 19.5.1.14 in the AM335X TRM Rev. L). You have to disable auto-RTS before this.

0 shammi kaplesh over 9 years ago in reply to Biser Gatchev-XID

Expert 1475 points

Can you tell me how to disable AutoRTS feature in omap-serial.c ?

0 Ivan Matrakov over 9 years ago in reply to shammi kaplesh

TI__Expert 4475 points

Hi Shammi,

In a sdk6 kernel you can do this in omap-serial.c in serial_omap_set_termios(...) procedure in about 878 line. You will see the comment: "/* Enable AUTORTS and AUTOCTS */" You can see which way is working and modify by your purpose.

In a sdk7 kernel the place is the same serial_omap_set_termios(...), but code (1009 and 1015 line) is small different. Also you can do some modification.

BR
Ivan

0 shammi kaplesh over 9 years ago in reply to Ivan Matrakov

Expert 1475 points

I have some confusion regarding RTS and CTS. RTS should be output line and CTS should be input line, But in am335evm RTS is configured as input and CTS as output.

Please clarify about this.

0 shammi kaplesh over 9 years ago in reply to Ivan Matrakov

Expert 1475 points

Hi i have some delay requirement in serial driver(Rs 232). Once the RTS line is raised, the processor will delay this amount of time before actually starting to send data(KEY UP TIME).
Is it possible?

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Hardware flow control in am335x problem