Hamlib: "ppdev0: claim the port first"
Howdy. I'm trying to use hamlib to control an Icom IC-746 with a homebrew TTL to RS232 level converter. The level converter works great on my dekstop's DB9 RS-232 serial port, but not on my laptop's DB25 RS-232 parallel port. Both run the same Debian Sarge release with very similar sets of software packages. The problem I'm having is that when any application tries to use the parallel port, ppdev gets angry. The specific error in the message log is:
"ppdev0: claim the port first"
Does anyone have an idea as to what this is alluding to? Google wasn't much help for me.
Cheers,
Jonathan Lassoff (KG6THI)
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Quoted 7 lines · Wilbert Knol
A level converter designed to work with EIA232 ports won't work on a parallel port. They are different beasts with different voltage levels and pin-outs.
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Hope this helps.Wilbert, ZL2BSJ
I realized about 10 minutes after sending that message that I made a mistake as to the different device architectures. Is there any crossover between the the parallel port design and the older RS-232 ports? Does the parallel port actually send the same data? The level converter uses the voltage from the DTR and RTS through a 5V regulator to power an IC that converts the TTL voltages to RS-232 levels and vice versa. Anyone have thoughts on the matter?
My next plan is to get a USB to DB9 serial converter. Only problem is that I can only find reliable information that says that the one from Radio Shack works with linux, and those cost like 40 bucks USD. I found one on eBay for $5 USD, but I'm not sure if it works. It's a model GWC UC320. Does anyone have any experience with it?
Cheers again,
Jonathan Lassoff (KG6THI)
Quoted 7 lines · On Tue, 26 Jul 2005 20:42:38 -0700 Jonathan Lassoff wrote:
Quoted 6 lines · Wilbert Knol
A level converter designed to work with EIA232 ports won't work on a parallel port. They are different beasts with different voltage levels and pin-outs.
...
Hope this helps.
Quoted 6 lines
Quoted 1 line
Wilbert, ZL2BSJ
I realized about 10 minutes after sending that message that I made a mistake as to the different device architectures. Is there any crossover between the the parallel port design and the older RS-232 ports? Does the parallel port actually send the same data?
Yes, but they work in a totally different way. Serial port sends it's data one bit at a time through the tx line, and parallel sends it all bits at the same time, using different lines.
Many applications don't even use the serial port as a serial device (transmitting data) but as a control device (such as soundmodem ptt control). In those cases, they generally use handshaking lines, instead of data lines. In those cases, you could use a parallel port, if the application can support it.
Quoted 3 lines
The level converter uses the voltage from the DTR and RTS through a 5V regulator to power an IC that converts the TTL voltages to RS-232 levels and vice versa. Anyone have thoughts on the matter?
I don't understand if you need ttl levels output or rs-232 level output. Standard serial port uses rs-232 levels. If you need ttl levels, you need a converter.
Parallel port, on the other hand, uses ttl levels. So, if your application supports using a parallel port, you don't need a converter. Notice that your program must have support for it, and cabling is different.