Using UART3

[lpcware]

Content originally posted in LPCWare by jbperkins on Sun Oct 30 13:16:58 MST 2011
I'm trying to modify the UART example from NXP_LPCXpresso1769_MCB1700_2011-02-11.zip to use UART3 instead of UART0.  It's not working.  Before I go any further let me start with simple question.

Is there something that I have to do to enable UART3?  I read something that made me think that UART3 defaults to off.  I tried setting bit 25 of PCONP to 1 (which should turn it on??) but that doesn't take.  When I looked at the PCONP register all of the UART bits where set to 0.

-Jim

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Mon Oct 31 19:14:55 MST 2011
Wow, 45 x 55 mm :eek:

Should be called Maxi Board :rolleyes:

[lpcware]

Content originally posted in LPCWare by jbperkins on Mon Oct 31 19:09:18 MST 2011
This should do the trick for the RS232 interface:
http://www.futurlec.com/Mini_RS232_TTL_3V.shtml

Got one of these too:
http://www.futurlec.com/Mini_SC.shtml

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Mon Oct 31 04:27:31 MST 2011
Of course you can also use a Pseudo RS232 (for lower speeds) like:

http://dave.fraildream.net/micro/periph/232-ttl.html

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Oct 30 20:23:07 MST 2011
Perhaps MAX3232 like page 8 of:

http://support.code-red-tech.com/Cod...ser+Manual.pdf

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Oct 30 20:22:01 MST 2011
Perhaps page 8 of:

http://support.code-red-tech.com/Cod...ser+Manual.pdf

[lpcware]

Content originally posted in LPCWare by jbperkins on Sun Oct 30 20:13:44 MST 2011
Yeah it was a few days back.  Now I'm good at Matlab and PowerPoint.....

Ok, so I need a line driver.  If all I wanted to do is receive from an RS232 source I could use a voltage divider.  I'll see what Maxim has for drivers.

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Oct 30 18:50:46 MST 2011

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Quote: jbperkins
I used to be good at this stuff..............

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Seems to be a few days back :)

You didn't really connect  3.3V P0[0]/P0[1] to RS232 and expect it to run :eek::eek:

Note #1: This sample is working as expected: Transmitting "UART3 Online:" via J6-9 (TXD3) and repeating every received byte from J6-10 (RXD3)

Note #2: Hyperterminal isn't very reliable, a free alternative is TeraTerm: http://ttssh2.sourceforge.jp/

[lpcware]

Content originally posted in LPCWare by jbperkins on Sun Oct 30 18:39:13 MST 2011
I just tried that example.  It compiles and runs but I don't get any output.  I figured this would be easy.  I attached a female DB9 to the LPCXpresso board as follows.

LPCXpresso     DB9
J6-1              -------> pin 5
J6-9                               -------> pin 2
J6-10            ------> pin 3

I plugged the female DB9 directly into a USB to RS232 adapter.  I ran Hyperterminal on the com port for the USB-RS232 adapter.  I know the USB-RS232 adapter works because I can short pin 2 to pin 3 and get characters to echo in Hyperterminal.  I also tried hooking J6-9 to pin 3 and J6-10 to pin 2.  That didn't work either. 

I used to be good at this stuff..............

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Oct 30 13:28:28 MST 2011

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Quote:

Is there something that I have to do to enable UART3?

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Yes, set PCONP bit (25) and change Pin function to RXD3/TXD3 in PINSEL register :)

Note: In UART sample of examples.lpc17xx.new.zip you can find an UartInit for UART3 in uart.c :rolleyes: