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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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 10 May 2008 11:41 Doubt with microcontroller connection. |
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Hello.
Im doing a project that connects a xbee with one microcontroller(pic16f88), now my doubt is if i connect the tx pin from xbee, with rx pin from pic directly, like the following image, the pic will receive the byte without erros? because the voltage in transmisons will be 3,3V and the pic works with 5V.
Regards.
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pakitos
Joined: 14 Nov 2005
Posts: 310
Helped: 38
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| 10 May 2008 11:50 Doubt with microcontroller connection. |
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| what i the question?
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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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| 10 May 2008 12:13 Re: Doubt with microcontroller connection. |
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| pakitos wrote: |
| what i the question? |
The question is, if the pic will receive the information correctly, because the pic works with TTL, and xbee send 3,3V.
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nandhu015
Joined: 11 Feb 2006
Posts: 346
Helped: 26
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| 10 May 2008 16:28 Re: Doubt with microcontroller connection. |
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It is not advisable to do so.
Nandhu
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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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| 10 May 2008 17:02 Re: Doubt with microcontroller connection. |
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| nandhu015 wrote: |
It is not advisable to do so.
Nandhu |
And what is the best way to connect tx from xbee with microcontroller RX??
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pakitos
Joined: 14 Nov 2005
Posts: 310
Helped: 38
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| 10 May 2008 20:52 Doubt with microcontroller connection. |
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I do not know why Nandu said so
but concerning the voltage the pic will accept the 3.3v as high.
If the Iout of the device < Iin of the pic no damage will happen. Which I think is the case.
give it a try
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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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| 10 May 2008 21:04 Re: Doubt with microcontroller connection. |
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| pakitos wrote: |
I do not know why Nandu said so
but concerning the voltage the pic will accept the 3.3v as high.
If the Iout of the device < Iin of the pic no damage will happen. Which I think is the case.
give it a try |
Thanks.i will try.
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nandhu015
Joined: 11 Feb 2006
Posts: 346
Helped: 26
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| 11 May 2008 4:28 Re: Doubt with microcontroller connection. |
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| pakitos wrote: |
I do not know why Nandu said so
but concerning the voltage the pic will accept the 3.3v as high.
If the Iout of the device < Iin of the pic no damage will happen. Which I think is the case.
give it a try |
does the zigbee can handle 5v at its input?
I personally will use a level convertor
Nandhu
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pakitos
Joined: 14 Nov 2005
Posts: 310
Helped: 38
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| 11 May 2008 19:02 Doubt with microcontroller connection. |
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| he is going to use the zigbee as input to microcontroller not the microcontroller input to zigbee Right?
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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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| 11 May 2008 19:15 Re: Doubt with microcontroller connection. |
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| pakitos wrote: |
| he is going to use the zigbee as input to microcontroller not the microcontroller input to zigbee Right? |
Thats it, to micro-xbee i use the resistors.
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pakitos
Joined: 14 Nov 2005
Posts: 310
Helped: 38
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| 12 May 2008 11:47 Doubt with microcontroller connection. |
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Ok let me guide you.
for the pic as TX you have used resistors.. These resistors will lower the voltage comming out of pic( 5V) to a lower level which can be handeled by Xbee.
As for the pic working as RX:
check first if the pic is considering the 3.3 voltage as high (simple test). ( I think it should)
If the pic is not receiving correctly, what you can do is use a transistor as switch bw xbee and pic
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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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| 12 May 2008 23:59 Re: Doubt with microcontroller connection. |
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| pakitos wrote: |
Ok let me guide you.
for the pic as TX you have used resistors.. These resistors will lower the voltage comming out of pic( 5V) to a lower level which can be handeled by Xbee.
As for the pic working as RX:
check first if the pic is considering the 3.3 voltage as high (simple test). ( I think it should)
If the pic is not receiving correctly, what you can do is use a transistor as switch bw xbee and pic |
thanks.Any more boubt i post .
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marcelino
Joined: 06 Jan 2006
Posts: 8
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| 07 Jul 2008 8:20 Doubt with microcontroller connection. |
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its the resistor!!! why din't i think of this...
tsk tsk tsk, i just broke one module! there should be a resistor...
so what are the typical values for resistor?
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Eraser
Joined: 02 Nov 2007
Posts: 49
Location: Braga,Portugal
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| 07 Jul 2008 18:49 Re: Doubt with microcontroller connection. |
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| There are not tipical resistors values, just make sure the resistors values are above 1kohm, because for values below 1k the current generated could be elevated, and damage the xbee. The voltage max. in xbee is 3,3V so you have to calculate the resistors. But in my post there are an image, 10k and 20k, for 5V.
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