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RS232/RS485 On the Cheap Print E-mail
After battling for a day trying to get my Animated Lighting RS232 to RS484 adapter to run with my new Renard hardware, I gave up and purchased 3 very inexpensive 232/485 converters and a very cheap USB to RS232 adapter.

In short, all 4 devices performed exceptionally at 115.2K with Vixen set to 25ms events on 48 Renard SS24 channels. 

All 4 of the devices were purchased from DealExtreme (DX), a Hong-Kong based supplier of electronics and gadgets.  In case you have reservations about ordering from China, I can personally recommend DX -  I've purchased many items from them over the course of 10 or so orders.  The trade off for cheap prices is speed.  It typically takes 2 to 3 weeks to receive your order.

For this test, I used this USB to RS232 adapter:  http://www.dealextreme.com/details.dx/sku.5859.  It was $4.66 shipped.  (July 2010 note:  The mfg has changed this adapter to use a different chipset, and I can't recommend this one any more.  Read more below.)

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... and these 3 RS232 to RS485 adapters:
http://www.dealextreme.com/details.dx/sku.5933 ($6.65 Shipped)
http://www.dealextreme.com/details.dx/sku.6040 ($5.66 Shipped)
http://www.dealextreme.com/details.dx/sku.9309 ($7.83 Shipped)

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If your computer already has a free serial (RS232 port), you don't need to use the USB to RS232 adapter, and can save even more money.  Just go from the free serial port to the RS485 adapter and you are done! 


To test these devices, I used my show computer;  A 4 year old Insignia (Best Buy brand) desktop:

P4 2.6 GHz
768 MB Ram
Windows XP Home SP3
1 On-board serial, 2 additional via PCI card
USB 2.0 ports

Two Renard SS24 boards were used to verify the communication.

This machine has 3 serial ports, 1 built in, 2 added with an internal PCI card.  Since I know these 3 COM ports work well (they were used with my Animated Lighting hardware), I used them to verify that I could successfully talk to the Renard Hardware at 19.2K, 57.6K, and finally at 115.2K using RS232.

Since I was successful at 115.2K, I set this as my benchmark.  Typically Renard hardware is run at 57.6K.  115.2K is the highest bit-rate that Vixen and the Renard firmware can handle, and since I wanted to stress the devices as much as I could, I selected it.  Remember that you will need to update the programming on your PIC micro-controller if you change bit-rates.  In the end I had recompiled the firmware to use the 115200 baud rate, and turned on the PWM mode (since this seems to be the new standard).

Once I was successfully talking to the boards using the on-board serial ports, I switched to the USB to RS232 adapter.  Rather than use the software that came with the device on the small CD, I went directly to the chip-set manufacturers website and downloaded the drivers there:

http://www.prolific.com.tw/eng/downloads.asp?ID=31 (July 2010: See below)

The DealExtreme website says that the device is not compatible with Vista or Vista 64 bit, however the mfg site claims that with the new drivers it is.  I did not test these claims.

Installation was a breeze:  unzip, run the EXE, plug the adapter into an available USB 2.0 port.  2 seconds later the adapter was installed as COM 5. 

Unfortunately, Vixen only works with COM1 - COM4.  You can change the port (XP) by going to Device Manager (Right click 'My Computer'/Properties/Hardware/Device Manager), and expanding the 'Ports (COM & LPT)' section.  Right click on the 'Prolific USB-to-Serial Comm Port', then Properties/Port Settings/Advanced.  Change the COM port number to one in the range COM1-COM4 that is available, then select OK - for me, COM3 was available.  You should also at this point change the Port settings to match the speed of your controller network.  In my case for this test, that was 115200/8/None/1/None.  The adapter was then directly connected to the first Renard SS24 board via the DB9 connector, and the second Renard SS24 was daisy chained with a normal Cat 5 cable.

UPDATE July 2010: 

Matt from DoItYourselfChristmas posted that the manufacturer of the USB to RS232 adapter has changed chipsets.  He tested several of them, and they do not output enough current and/or correct voltage to directly work with the RS232 to RS485 adapters.  If you use this particular adapter, you'll need to feed +5v to the RS232 to RS485 adapter's external power connector (see below). 

Naturally, the link I posted above for drivers will NOT work with this new adapter. 

There is no problem with the RS232 to RS485 adapters, just with low voltage/amperage from the USB to RS232.

I created a new sequence in Vixen for 48 channels using 25ms events.  I set up the Renard plug-in to use COM3, 115.2K.  I lit channel 1 solid, and blinked channel 25 (on the second board) every other column.  The test ran flawlessly.

Since this test ran so well, I did not bother trying to use the RS485 adapters with the on-board serial ports.  Instead, I kept using the USB serial port. 


All 3 RS485 adapters come with a small circuit board with screw terminals to hook up the communications wire.  I used a 5 foot piece of Cat5e cable, and hooked up the white with blue stripe wire to the terminal marked D+ or A, and the solid blue wire to the D- or B terminal. 

All 3 adapters also have connectors for external power.  I did not use these terminals.  However, you may need to supply external power if using a laptop (since USB ports on laptops tend to be low power), or if your initial run from the computer to your first board is long.  When I set up for 2009, I'll have a better idea on if external power is needed for my 150 foot first run.

One of the adapters has connections for RXD+ and RXD-.  These terminals are typically used in full-duplex setups.  I did not test them, nor do I know if they are even functional.

Differences between the 3 models:


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5933 is made by U-Tek, and came packaged in a plastic blister pack.  It has the aforementioned RXD terminals.  It appears to be well built, and the breakout board has a nice right-angle DB9.  It came with very limited instructions.


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9309 is made by SinTec.  It was nicely packaged in a box with a foam insert.  According to the breakout board, this is their 'Industrial Converter'.  It appears to be well built with A right angle DB9.  No English instructions.  


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6040 is also made by SinTech, with a model number of STM485S.  This is actually a different model than what is shown on the DX site.  The actual converter is identical in shape/size as the 9309, except it is in cream and the other is black.  It too was nicely packaged in a box with foam insert, but again it had no instructions.  The major difference with this version and the 9309 is the breakout board.  It's much smaller and doesn't use a right angle DB9.  Instead, a regular solderable DB9 is used, with the circuit board jammed between the rows of pins.  The pins are then directly soldered to the top/bottom of the breakout board.  Since the board hangs in the air, with the strain of the cable the solder points could eventually break.

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Once again, all 3 performed flawlessly with no detected errors. 

For one additional test, I took the Beta Renard Diagnostic Firmware, and recompiled it to use 115.2K.  Once the PIC stoped testing the channels, only the HB and ZC LEDs flash.  At this point I re-ran my Vixen test 10 times, carefully observing the FE (framing error) and OE (over-run error) lights.  At no time did I see either light, while the SD light was solid.


Conclusion:

All 4 devices worked for me, with no problems, all the way to the max data rate of 115.2K.  However, this was a very limited test with only 48 channels, using short cables, and only using Renard SS24 hardware. 

While you can have a working setup for just over $10 shipped by using the 6040 RS485 converter, I suggest you spend the extra $2.20 (for a total of under $13) and purchase the 9309. 

 
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