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Serial input into Board of education need 22kOhm resistor or MAX232? — Parallax Forums

Serial input into Board of education need 22kOhm resistor or MAX232?

OrangeOrange Posts: 14
edited 2007-10-23 04:23 in BASIC Stamp
I have a BS2-IC Board of education and i want to input serial data (12V) to the input pins.

From the manual SERIN, it seems like we only need to connect pin 3 at DB9 a 22kOhm resistor in order to step down into TTL voltage.

But somebody told me that a max232 (with all the resistors and capacitors) TTL to RS232 converter kit is needed.

So what do I actually need? The resistor only or the max232?

Thanks.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-10-20 05:08
    The 22K resistor will work very nicely for input only. For output and input, a MAX232 would be better since it can generate the voltages needed. It also conditions the signals (like slewing control). The 22K resistor provides a lot of protection for the Stamp. the MAX232 is specifically designed to protect the UART or microcontroller.
  • OrangeOrange Posts: 14
    edited 2007-10-20 07:00
    Huge thanks!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-10-22 17:15
    Bear in mind that using the resistor the signal will not be inverted whereas using the MAX232 it will be inverted. Take care.

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    Chris Savage
    Parallax Tech Support
  • OrangeOrange Posts: 14
    edited 2007-10-23 04:23
    Many thanks!
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