UART communication

[lpcware]

Content originally posted in LPCWare by m22 on Tue Oct 25 12:03:06 MST 2011
Hello,

I'm a newbie and I'm trying to communicate with a Xbee module thanks to my LPCXpresso board using a UART. The chip on my board is a lpc1114. I am currently facing some issues when sending data. The TXD pin is continuously at a high level. I was wondering if it could be due to the output voltage which could be too low (it must be at least 2.6 V for Xbee input). I'm  using  code inspired by the UART example and it worked once...

Thanks for any reply!

[lpcware]

Content originally posted in LPCWare by Polux rsv on Thu Oct 27 14:54:14 MST 2011

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Quote: Zero
50 baud

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:D Even the worst voltmeter will show something.

Angelo

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Thu Oct 27 09:52:40 MST 2011

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Quote: Polux rsv
And even with a good transmission, a simple voltmeter could measure a high value.

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Therefore it's a good idea to use a simple LED with 1k resistor to 3.3V :eek:

Init with 50 baud will result in 180ms low while transmitting 0x00 :)

[lpcware]

Content originally posted in LPCWare by Polux rsv on Thu Oct 27 09:19:56 MST 2011
Idle state of an uart line is high, not low.
And even with a good transmission, a simple voltmeter could measure a high value. Use a scope to be sure of what is appening on the lines.

Angelo

[lpcware]

Content originally posted in LPCWare by NXP_Europe on Wed Oct 26 08:05:15 MST 2011

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Quote: m22
Hello,

I'm a newbie and I'm trying to communicate with a Xbee module thanks to my LPCXpresso board using a UART. The chip on my board is a lpc1114. I am currently facing some issues when sending data. The TXD pin is continuously at a high level. I was wondering if it could be due to the output voltage which could be too low (it must be at least 2.6 V for Xbee input). I'm  using  code inspired by the UART example and it worked once...

Thanks for any reply!

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Hi,
Above text is not sufficient to understand your problem. If you are using the same code as of UART example then you should see your message on TXD line. It would be nice if you include listing of your code in next post.

Kind Regards,

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Wed Oct 26 03:47:57 MST 2011
So did you scope your TxD (of LPCXpresso) while you are sending data via UART and it's always high?

Then I would suggest to disconnect everything from this pin. If it isn't showing your UART message your UART isn't working :eek:

[lpcware]

Content originally posted in LPCWare by m22 on Wed Oct 26 03:14:13 MST 2011
yes,sorry for my bad english...

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Tue Oct 25 12:42:21 MST 2011

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Quote: m22
...The TXD pin is continuously at a high level

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TxD of LPCXpresso is always high?