Lpc2000

Hi Sten,

Thanks for your reply. Yes, this is what I'm doing now with the PIC chip 
and was expecting to have to do on the Arm. As I'm new to it, I wasn't 
sure if there was a neater way to do it. I moving (Trying to) to the Arm 
for more Grunt.

Cheers,

peter

Sten wrote:
> Peter Homann wrote:
> 
>>Hi,
>>
>>I am migrating a serial communications interface (Modbus) to a LPC2138 
>>processor. The Modbus spec defines that an end of message has occurred 
>>when a period equal to 3.5 characters has passed since the last 
>>character has been received.
>>
>>The LPC uart can generate an interrupt if the receive buffer has 
>>characters in it and no character has been received for a period of 3.5 
>>- 4.5 characters.
>>
>>I would like to use this feature for detecting the end of a received 
>>message. The problem I have is that if I service an interrupt due the 
>>the buffer being filled, and it also happens that that last character in 
>>the buffer was the last character for the received message, the receive 
>>time-out interrupt will not occur, resulting in the end of message not 
>>being detected.
>>
>>Is there a solution, other than using a buffer length of 1 and using a 
>>timer to measure the inter message gap?
>>
>>Cheers,
>>
>>Peter.
>>
> 
> 
> Hello Peter,
> 
> this interrupt was not designed for your needs. It should prevent a
> communication from being stalled if some characters are trapped in queue
> which is not full.
> Just an idea: every time you receive a character reset a timer. If a
> timer interrupt occure prior a line idle interrupt, you have not
> received any characters for a certain time. It's ugly but should solve
> your problem.
> 
>   Sten
> 

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