> On Wednesday 06 Feb 2013, Brendan Simon (eTRIX) wrote:
>> I'm looking for a very small and very low cost SBC with a USB host port,
>> serial port (UART or RS485) and Ethernet (10 or 10/100).  The purpose is
>> to bridge between two systems -- one system is a piece of equipment that
>> only has a USB device port (serial protocol) and the other is a master
>> controller which can have Ethernet and/or RS485.
>>
>> I was hoping to also add other services such as :- web browser, FTP
>> server, etc, which led me towards an openwrt solution as possibility.
>>
>> The best board I've come up with is a TP-Link TL-WR703N.  It is cheap,
>> has Ethernet (and wifi) and an internal serial, but the internal serial
>> is just a couple of pads (I'd prefer a proper connector) and I'm not
>> sure I can modify it for RS485 (e.g. provision for a Tx/Rx enable
>> signal).  Two serial ports and/or two usb ports would be nice but not
>> necessary.
>>
>> I was wondering if anyone could suggest other boards/products to look at :)
>>
>> Thanks, Brendan.
> Have you looked at the carambola?  The current version has some problems
> with USB (earthing problems on the shield), but a new version is due this
> month.  They use a version of OpenWRT as firmware.

Haven't come across the Carambola.  It looks interesting and reasonably
priced.  Main features are 2 x Eth LAN (10/100 I presume), 1 x WLAN
(802.11bgn), USB OTG, 2 x UART, SPI and I2C.  It certainly could do the
job.  Price 22 euro, down to 17 euro in quantities of 100.

According to openwrt site, I found that TP-Link TL-MR3020 is almost
identical to the TL-WR703N (I actually have no idea what the difference
is.  maybe just the switch on the side ??) but it has a 4 pin internal
serial connector.  I can buy this in Australia at a retail store for
around A$35.  I've seen the WR703N in China wholesale sites for under
US$20.  I would think it should be possible to source MR3020 for under
US$30 (tho I've only found them around US$60 which makes no sense).

Another alternative is the RaspberryPi (1 x Eth Lan, 2 x USB, GPIO
connector with UART, SPI, I2C) at around A$36.

Finally, found a 16-bit PIC board (NetCruzer) with Eth Lan, USB OTG, and
2 IO connectors with mappable GPIO/peripherals (4 uarts, 9 pwm, 2 spi, 2
i2c).

Cheers, Brendan.

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