Most modern AVRs include at least one hardware USART (or USI in some cases).
Many have multiple instances.
I am trying to determine how often these multiple instances are actually used.
By 'actually used' is meant, in deployed applications.
Yeah I know when you bought that Arduino Mega, you played with all the USARTS, perhaps (as I did) you daisy chained them and measured the over all latency.
That's not a deployed application, but... interesting.
Thanks for your participation!
If you are controlling 4 serial gizmos, you get a computer with 4 serial ports. That aint rocket science.
I hope all the folks who have never "deployed" anything put down zero.
Jim
Most of the time 1 or two uarts are adequate. sometimes you can never get enough. One project I did had two GNSS receivers, uhf tranceiver,telemetry receiver, port to the PC. Loosely you could equate the number of uarts with available ram - one would expect with 8 uarts you want enough ram to have some nice buffering. Putting 8 uarts on a device with 1K of ram is probably stretching the friendship whereas 8K or more is more sensible.
I hope all the folks who have never "deployed" anything put down zero.
This reminds me of a thread I had about the amount of flash memory being too much. For example, I am using a Tiny1634 because I needed the two USARTS but I sure do not need 16k of flash. Lee's comment of basically "So What" made sense. So what if the AVR has 4 usarts. If you don't need all four, but the device has something else in it you do need and no other AVR does then do not use the usarts. They are there for Rev 2.0 ;)
I would have at least 2 usarts in every MCU I use. One port for RS-485 network and another one for debug console. That's is pretty :) Unfortunately, most controllers that I have don't contain them. Only one(
I have used 4 in some application.
RS232 for debug/parameter setting etc.
RS232 for another device.
RS422 for some part of the system.
RS485 for other part of the system.
Something in excess of 1500 (2 x T3 dialin server.)
(I don't think that that one used any AVRs, though. And probably not USARTs in the conventional sense, either...
For real UARTS, it was only about 100, on more traditional terminal servers.)
I used two 6402-style UARTs on my first project out of college, to convert a 6bit 75bps newswire feed to the 8bit 300bps data that the mainframe would accept. If there had been microcontrollers around at the time, it could have done the ascii conversion as well.
In some sense, I like the Basic Stamp philosophy - every pin should be able to send serial data, because it's easier to add intelligence to your peripheral than pins to your chip... (which probably isn't true, but it's ok as a philosophy.)
Driving multiple serial ports "at speed" is surprisingly difficult. :-(
I imagine you'll get quite a few "3" from those developing a location device that has GPS on one, GSM on another and a control/debug interface on a third.
(interesting to note that the LPC800 range have been designed with 3. I imagine quite a lot of research went into that decision).
In the last year, I have had 4 deployed applications using zero UARTs and 1 with two UARTs. What do I put down? The 0-UART ones have a far higher production volume than the 2-UART one.
Jim
I did a board with 140 uarts plus one for the console port for a piece of test equipment (the whole tester had over 6400 uarts in it). My current board has one.
/mike
For some reason, the zero option does not show up!
I imagine quite a lot of research went into that decision
Well, despite the fact that I lost my bet :shock: , thanks to the freaks who responded!
I had expected that by far, a single usart would fill the bill, if any were needed at all. Though the poll is not-even scientific, the comments pretty much back up the numbers.
Personally the most I ever deployed at a time was an industrial control 'aggregator', mastering 8 RS-485 busses.
We sent out a little board with a 1280 on it that used all 4 uarts... 0 went to a Lantronix Xport at 230400 bps 1 went to a StormScope at 9600 bps, 2 went to a GPS at 4800 bps, 3 went to a debug port at 115200.
I would have voted, but there wasn't a "I hate USARTS" option.
