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scarr
Joined: 15 Nov 2003
Posts: 4
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| Simple, small, PIC to rs232 converter |
 Posted: Sat Mar 13, 2004 4:34 am |
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Hi,
I am looking for a simple and easy ideally single IC that can convert PIC rs232 to standard rs232 (PC) no flow control just the TX line from my PIC.
Thx |
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Ttelmah
Guest
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| Re: Simple, small, PIC to rs232 converter |
| Posted: Sat Mar 13, 2004 4:56 am |
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| scarr wrote: | Hi,
I am looking for a simple and easy ideally single IC that can convert PIC rs232 to standard rs232 (PC) no flow control just the TX line from my PIC.
Thx |
Look at the DS275 from Dallas.
However this really needs the RX line from the PC connected as well. It achieves 'nearly' standard RS232 levels, but I have yet to find anything that complains about them, by stealing power from the RX line. For systems needing both a TX and RX line, it is probably about as simple as you can get. However for a single TX 'only' system, the problem is that you need to generate the -ve supply from somewhere, so will probably end up with more complexity.
Best Wishes |
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Lestard
Joined: 13 Mar 2004
Posts: 2
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| RE: Simple converter |
| Posted: Sat Mar 13, 2004 12:36 pm |
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You can also use a MAX232 from MaximIC.
This is a small IC which converts normal TTL (PIC)-level (0V and +5V)
to RS232-level (-10V and +10V).
You only need a normal +5V supply and some capacitors, and if you
need only 2 or 3 converters, just ask MaximIC for some free samples! |
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Ttelmah
Guest
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| Re: RE: Simple converter |
| Posted: Sat Mar 13, 2004 12:40 pm |
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| Lestard wrote: | You can also use a MAX232 from MaximIC.
This is a small IC which converts normal TTL (PIC)-level (0V and +5V)
to RS232-level (-10V and +10V).
You only need a normal +5V supply and some capacitors, and if you
need only 2 or 3 converters, just ask MaximIC for some free samples! |
This is the 'standard' solution, but is not a 'small' IC (16pin). The MAX233, is normally preferred (since it needs no external capacitors). I was assuming that something smaller is required.
Best Wishes |
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Freddie
Joined: 06 Sep 2003
Posts: 49
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| Posted: Sat Mar 13, 2004 1:33 pm |
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You can connect the PIC to a PC serial port without using a MAX232/233 or Dallas Chip. There are several clever ways to do this with only a resistor, but I've notices that those methods can limit the bandwidth.
There is another way, using two transistors. Go to the link below. Look at page 16, specifically the circuits connected to pins 5 and 6 of the elm320 chip (the elm320 is just a PIC). Pin 5 is Rx and Pin6 is Tx. This schematic assumes a DB25 on the PC. If you are using the D9, you will need to adjust accordingly, using pins 2,3 and 5...can't remember off hand if tx is pin 2 or 3 on the DB9. Hope this helps.
http://www.elmelectronics.com/DSheets/ELM320DS.pdf |
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dyeatman
Joined: 06 Sep 2003
Posts: 1912
Location: Norman, OK
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| RS232 Interface |
| Posted: Sat Mar 13, 2004 3:48 pm |
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One thing to remember is that you must invert the PIC hardware RS232 Transmit signal for it to work to a PC serial port. This can be done with a simple SN7404 TTL inverter which i have used a number of times for "quick and dirty" and you dont need anything but the inverter. However, for the receive to the PIC the +/-12V will be incompatible with the SN7404 input so you will need a resistor divider there.
The transisitor interface method Freddie mentioned gives you the inverter function and the level change interface and works well but requires a few more parts. |
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