Question about ARRAYWRITE

**aratti** · - 29th July 2010, 12:27

With one USART and DT interrupt and using a RS485 ring, you can connect several devices at a pretty high speed. Look the data sheet for 75176 (there are several others, but I use this one) for more detail.

Al.

**HenrikOlsson** · - 29th July 2010, 12:38

Hi Al,
Yes, that's possible, as long as you have control over the transmitting devices or if you don't care if you miss some data by cycling thru the devices listening to one device at a time. If they are self contained units sending data on their own, at will, then it's going to be tricky. If I've missed your point please enlighten me :-)

Now, the OP doesn't say how the transmitting devices works and/or if he has "control" over how they works. Hopefully a multidrop network can be implemented in which case one USART would be enough.

/Henrik.

**aratti** · - 29th July 2010, 13:41

Yes, that's possible, as long as you have control over the transmitting devices

Yes, Henrik the control is necessary, devices must tx only on request, without it the OP will not achieve much.

Al.

**circuitpro** · - 29th July 2010, 16:27

Thanks for the info! This particular application is a polled system, and my local PIC needs to process data and format the output into a predefined 'message'. Then when I am polled, I need to forward the data on to the host. I think ARRAYWRITE is the way to go. I was thinking about using an eeprom, but this is definately faster. I am not sure of the time between the polls yet though, and am concerned my data will back up, so need some message buffer space. Thanks very much for your help.

**circuitpro** · - 30th July 2010, 00:37

One interesting thing...

It seems that ARRAYWRITE does not work with indexed variables.

ARRAYWRITE MSG ["VALUE: ",DEC TMR[X]]

I'm just copying the value of TMR[X] to another variable first for now. Is this a bug, or just not accounted for or ??? Great command nonetheless.