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Calculator Tech Support =>
Technology & Calculator Open Topic
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benryves
Active Member
Joined: 23 Feb 2006
Posts: 564
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 Posted: 16 Jan 2008 06:43:07 am Post subject: |
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Well, it's too late as you did try it, but I'll mention it here just for future reference; do NOT use the jack-plug style serial port cables with TIs! They are just direct connections to serial port input and output lines, and RS-232 operates at a TI-frying 12V signal level.
The TI's protocol is nothing to do with RS-232. The use of the COM port is closer to using a parallel port (hence the parallel port cable design is much simpler than the $4 link) - the computer software sets or resets the state of individual pins (which is why cheap USB-to-serial adapters don't tend to work) and doesn't use a time-based signal at all.
Of course, they could have installed a hardware UART, but they did at least offer an adapter between RS-232 and their own protocol in the form of the greylink cable.
Edit: Even more confusingly, the camera cables are wired in an unexpected manner for those used to audio connections, where the tip of the plug is usually ground (rather than the base). PICAXE microcontrollers use the same cables, and it's all too easy to damage a chip by accidentally miswiring the serial cable jack socket.
Last edited by Guest on 17 Jan 2008 06:17:25 am; edited 1 time in total |
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DigiTan
Unregistered HyperCam 2
Super Elite (Last Title)
Joined: 10 Nov 2003
Posts: 4468
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| Posted: 16 Jan 2008 02:54:58 pm Post subject: |
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Yeah, if the tip is grounded, it's definitely a trouble-maker. With $15 and an ebay account, that's one headache gone right there.
There's also quick trick to getting around the +/- 12V problem. If tunneling diodes are placed on the TI side of the link, they'll clip the RS-232 voltage down to 0V - 5V or whatever the preference may be. Then the TXD line can be used as a negative voltage source. The downside is this only leaves you a 2-Volt noise margin compared to the usual 9. So the cable length suffers. I don't know if it's something StudioMadcrow would be interested in though.
Last edited by Guest on 16 Jan 2008 03:25:09 pm; edited 1 time in total |
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StudioMadcrow
Newbie
Joined: 11 Jan 2008
Posts: 13
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| Posted: 18 Jan 2008 12:27:40 pm Post subject: |
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| Well, I guess I'll never try that again (luckily my TI isn't fried from the previous attempt) |
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