3x USART <-> Ethernet through Colibri Linux module - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: July 11, 2018, 09:52:48 am
content: Hi guys,I've got an application that's got three different serial lines (at logic levels) from various blocks and I need to connect it to Ethernet. Two of them are slow management lines ( ~1kB/sec max), but one is pretty fast - 170kB/sec max (but only one way (Device -> Ethernet)). This can be used when using a custom baud rate, so hardware wise it is not be a problem.I want to use a dedicated module for this, and we've had good experience with Toradex Colibri modules in the past, namely the VF50 (https://www.toradex.com/computer-on-modules/colibri-arm-family/nxp-freescale-vybrid-vf5xx) and VF61.The Ethernet line is a dedicated line between the device and a receiving computer. As such the modules would be acting as a glorified Serial<->Ethernet converter. A small server application would be written to do the talking (or maybe just a few one of those magic Linux commands would do maybe?). Ideally I would just connect to an address, it would have three ports available and that's it.My question is whether you think that these data rates are achievable with all of the overhead that an OS will add to this, without custom drivers? I contacted Toradex support, they said that it should work, provided that I use handshaking during the serial communication, which I can do, but it implies that there might be some kind of issue?Thanks,David

author: ajb
author_rank: Super Contributor
timestamp: July 11, 2018, 06:01:17 pm
content: Is there a reason you want to do a custom device instead of an off-the-shelf serial to ethernet adapter?Random google result for example:http://us.brainboxes.com/product/es-701/4-port-rs232-ethernet-to-serial-adapter

author: daqq
author_rank: Super Contributor
timestamp: July 11, 2018, 07:41:01 pm
content: QuoteSize (the module will fit inside of the device, the device will fit inside of the example you provided), voltage levels (3.3V -> 3.3V, instead of 3.3V -> RS232), data rate, power consumption...I don'twantto do a custom, but at the moment it seems the best option - I'm hoping that using Linux it will be pretty straight forward, ideally just some minimal code.I know that there's a lot of off the shelf solutions where you get one UART, or where you get multiple RS232 lines, but none of them fit exactly.

author: andersm
author_rank: Super Contributor
timestamp: July 11, 2018, 08:32:32 pm
content: The least effort on the embedded side might be to just open 3 SSH connections, and run a terminal application in each. Since Linux isn't an RTOS (at least without a lot of tuning), there will be risk of the occasional dropped character, but then again data loss is always a risk in networked applications.

author: MatjazB
author_rank: Newbie
timestamp: July 12, 2018, 06:10:37 am
content: You can take a look atLantronix XPortdevices. But you will need one device for each serial channel (or they have multi serial device).If you want to DIY then you can take a look into ESP8266 direction. Something likeesp-link. But you have a lot of such things (even with many serial ports).

author: daqq
author_rank: Super Contributor
timestamp: July 12, 2018, 09:44:38 am
content: Thanks, I've already taken a look at the Xport device. The problem there is its low baud rate, as well as the fact that I would have to use three devices, and I have only one Ethernet connection available.

author: Gribo
author_rank: Frequent Contributor
timestamp: July 12, 2018, 01:27:14 pm
content: If you can change your board layout, The xPico has 2 UARTs that can go up to 900Kbps. IIRC, it is more expensive than the xPort. Digi also has similar modules (ME9210).