| 3 Mbps RS232 converter or adapter I'm looking for a 3 Mbps USB to RS232 converter (preferred), or a low profile PCI or PCI-e card. Apparently (see »accesio.com/go.cgi?p=/press/PR-100714-1.html ) around 1 Mbps in general is the cutoff for R232 while 422/485 can go up to 3 Mbps.
Does anyone know a source for a 3 Mbps RS232 card or converter?
TIA
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Wacky Races 2012! |
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| Highest speed RS232 driver on Mouser only goes to 1M.
My guess is that you won't find such high speed. In all honesty I haven't seen any device doing over 115k. Capacitance of the cable becomes a major issue at higher baud rates. |
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| Maxim has 3 Mbps transceivers, so that is covered.
I think some of the fastest UARTs can also go that fast, either with external clock or custom programming.
Cable length should be under 3ft, but if needed, I can live with 1ft.
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Wacky Races 2012! |
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| Why do you want RS232? Is network an option? Or straight USB? |
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| I want to sniff on a 3 Mbps SLIP line in an embedded system...
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| reply to aurgathor
I have a feeling your best bet would be building a custom adapter to just capture data to a buffer and then dump it through a "regular" serial port. I would guess that the data on the line has TTL levels and that means the polarity is inverted... |
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| The signaling is 3.3V -- pretty much normal and shouldn't matter.
I'm actually thinking about using RS-422 or 485 for acquistion -- there are 3 Mbps cards for those, some from the aforementioned accessio, for example.
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| You want TTL serial, not RS-232. RS-232 uses about +/-10v and is only good to about 1MBaud. Grab a USB breakout based on a FTDI FT232R or similar chip such as this one and you should be golden.
/M |
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| Good find. Now, I just need to find an adapter that uses this chip and do not cripple it in any way. |
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| What's wrong with the board I posted? Perhaps if you described what exactly you're trying to build a bit better I can make some suggestions. From what you've posted it sounds like you're trying to do something like:
[3.3v embedded device]->[TTL to RS-232 adaptor]->several feet of cable->[RS-232 card in computer]
Is that correct? I don't think RS-232 is going to work very well at 3MBaud due to cable capacitance and the switching between +10v and -10v... If it's only 1'-3' why don't you just skip the RS-232 altogether and just use USB?
/M |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
1 edit | said by mackey:What's wrong with the board I posted?
Target customer is quite different for that sparkfun board which was designed mainly to break out the pins for debugging. It may not work at very high baud rates.
However, the tiny UB232R module was designed by FTDI engineers to support max datasheet rate of 3Mbaud in either TTL or RS232 mode. It is also available in their on-line store. 
»www.ftdichip.com/Support/Documen···232R.pdf |
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| said by lutful:said by mackey:What's wrong with the board I posted?
Target customer is quite different for that sparkfun board which was designed mainly to break out the pins for debugging. It may not work at very high baud rates. However, the tiny UB232R module was designed by FTDI engineers to support max datasheet rate of 3Mbaud in either TTL or RS232 mode. It is also available in their on-line store. » www.ftdichip.com/Support/Documen···232R.pdf I see absolutely no different between those 2 breakout boards other then the SparkFun one has all the handshaking lines also brought out.
The UB232R does NOT do RS-232 without an external level shifter, just like the SparkFun one. Other then voltage levels there is no difference between TTL and RS-232.
/M |
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