Re: [ts-7000] TS-7550 XUARTs

[Walter Marvin <>]

What actually occurs is that Technologic mmaps the xuart hardware into the Linux user space and then treats them as internal TCP servers.

They have arranged the servers so as to support "raw" device mapping within Linux. What this does is cause excessive user space to kernel space context switches, especially since the xuart hardware can dribble in characters a few time. This causes non-linear latency responses when combined with other user space loads.  The actual latency starts at about 2ms and increases in a non-linear fashion dependent on other load. This is really not that measurable with a simplistic program, but  top is useful.

If you want to use one xuart channel per serial line at 100 ms per packet, Technologics' system can probably handle that,  but I would model it with some scripting and measure, just to be sure

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From: mike ingle <>
To:
Sent: Wednesday, August 31, 2011 4:19 PM
Subject: Re: [ts-7000] TS-7550 XUARTs

 

Hi Walter,

Am I right there there is no device driver, and that the userspace just mmaps the xuarts?  For my application, latency won't be a problem, also very much a fixed line setup.  What little I read on the xuart indicated that they expect about 100ms latency in their user space server (I would assume that I wouldn't be using their xuartctl server, instead directly reading and writing to the xuarts) .  As long as It never ever drops characters, latency is OK.  Given how few of these will be built, and the desire to run device test routines on the server, I think 8 uarts per 7550 is OK.  my biggest concern is that the 7550 perform as described.

best regards Mike

On Aug 31, 2011, at 11:50 AM, Walter Marvin wrote:

 

The TS7500 and 7550 does NOT I repeat NOT have standard Linux serial device driver support. The User Space servers that Technologic supply limit the throughput and latency you achieve.  Since your baud rate is the same on all channels and the through put is relatively low you might be able to get away with it.  I would suggest you set up a demo with one 7550 and see if it works without delays. 

I had to modify the servers and finally write my own drivers to get 50 ms latency and line set up flexibility. If you go to a device driver, you might be able to multiplex the serial streams in hardware and limit the number of 7550's. I can help you with this.

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From: mike ingle <m("gmail.com","finndmike62");" target="_blank" href="">>
To: m("yahoogroups.com","ts-7000");" target="_blank" href="">
Sent: Wednesday, August 31, 2011 2:34 PM
Subject: [ts-7000] TS-7550 XUARTs

 

Hi all,

I need to maintain communications with 80 devices overRS-232 serial (115k). Each device streams an approximately 120 byte packet every 100ms.
also the host, can send packets, and expect a response at any time. The packets are hex encoded with out of band start and stop characters.

I am contemplating using 10 ts-7550s (with appropriate level shifters) to control the devices, and forward the data over ethernet. The intent would be to crack the serial packets (which include 2 crc32 checks) down to their 60byte binary size, buffer 10 or so serial packets per channel, (600bytes per ethernet packet) and send them on up to a host for logging and display.

My data rate calculations show very modest ethernet usage (8 x 600 bytes/s).

On the surface the ts-7550 looks like a nice fit for this. Anyone have any experience with the XUARTs , or better suggestions? Probably no more than 3 <80 channel systems> will be built.

Best Regards Mike

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