LK204-7T-1U Keypad Question

LK/ELK/VK/PK/OK/MX/GLK/EGLK/GVK/GLT Series

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wildstoats
LCD?
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Joined: Sun Jul 25, 2010 11:46 pm

LK204-7T-1U Keypad Question

Post by wildstoats » Mon Jul 26, 2010 8:43 am

Hello,

I am looking at using the LK204-7T (Non-USB) for one of my projects. I am using a microcontroller that provides dead simple 0-5V TTL for I/O which I understand will work with your LCD by swapping the resistors on the back from RS232 to TTL. However after reading the section describing the keypad I saw no mention of the TTL interface. Is this because the keypad is only supported via RS232 / I2C? If so I would much prefer to use some form of TTL to RS232 conversion circuit, which raises another question. In the documentation it states:

"The LK204-7T-1U provides a DB-9 Connector to readily interface with serial devices which use the EIA232 standard signal levels of +/-30V."

I don't believe I follow. I didn't think +/- 30V was within the defined spec for RS232 / EIA232. Typical ranges being between +/-5V to +/-15V. Admittedly I am a noobie to circuit design and electrical engineering in general but if you could shed some light on this or even just point me in the direction of some decent reading materials I would be much obliged.

Regards,
-B

Clark
Matrix Orbital
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Post by Clark » Mon Jul 26, 2010 9:36 am

Hello B,

My apologies for the confusion, when this manual comes up for a re-write I will take a look at some of the language used here. First, where RS-232 is used in the keypad description with regard to polling, it is a reference to both serial protocols. Our display will send back responses automatically on the serial bus by default; I2C users will need to disable that function. The keypad will definitely work in TTL mode.

Second, the RS-232 levels stated are merely a maximum, any proper RS-232 signal, up to those voltages, will be accepted. For a very basic reference to get you started, the Wikipedia article is satisfactory.

And as always, if you have any further questions or concerns we have a great forum community here to lend a hand.

Thanks,
~Troy
Troy Clark
Design & Development
Matrix Orbital

wildstoats
LCD?
Posts: 2
Joined: Sun Jul 25, 2010 11:46 pm

Post by wildstoats » Mon Jul 26, 2010 1:38 pm

That was incredibly helpful! Thank you for the quick reply!

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