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Author Topic: DTMF MT8870 with arduino for robot  (Read 803 times)
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qwerty156
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« on: October 10, 2012, 12:36:12 am »
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Hi,
I have attached my arduino to a MT8870 like in the following diagram:
http://www.pablin.com.ar/electron/circuito/telefon/decdtmf/circuito.gif

Problem is that only one column of keys seems to work. This column changes from phone to phone- I have tested this with 2 phones.
I have not installed any pull up/pull down resistors and nor is there any buffering b/w the outputs of the MT8870 and arduino, i.e. they are connected directly. Any plausible reason why this is not working?
Thanks
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kg4wsv
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« Reply #1 on: October 10, 2012, 07:40:12 am »
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code? actual schematic in use?

-j
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Graynomad
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« Reply #2 on: October 10, 2012, 07:45:34 am »
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You should have resisters because the outputs go tri-state when no signal is present, I'd use the internal pullup ones. Buffers should not be required.

What have you got StD connected to? And post your code.

______
Rob
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Rob Gray aka the GRAYnomad http://www.robgray.com

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