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Pic16F88
Checking pin voltages Portb pins read 5vdc and Porta pins read 2.5
vdc.
Why is this? On another circuit somewhat similar to this, I get 5vdc
readings on both Portb and Porta.
Thanks
bill



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PortA may be in analog mode or in high impedence (floating) state

Quoting wdavis364 :

> Pic16F88
> Checking pin voltages Portb pins read 5vdc and Porta pins read 2.5
> vdc.
> Why is this? On another circuit somewhat similar to this, I get 5vdc
> readings on both Portb and Porta.
> Thanks
> bill
>



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----- Original Message -----
From: "wdavis364"
To:
Sent: Wednesday, January 17, 2007 9:32 PM
Subject: [piclist] Portb pins 5v, Porta pins 2.5v ?
> Pic16F88
> Checking pin voltages Portb pins read 5vdc and Porta pins read 2.5
> vdc.
> Why is this? On another circuit somewhat similar to this, I get 5vdc
> readings on both Portb and Porta.

Have you enabled them all for digital I/O, ADC pins default to analogue
inputs, not digital.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
l...@btinternet.com
http://www.geocities.com/leon_heller


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Ok, I'll check it out.
thanks
----- Original Message -----
From: d...@hiwaay.net
To: p...@yahoogroups.com
Sent: Wednesday, January 17, 2007 3:42 PM
Subject: Re: [piclist] Portb pins 5v, Porta pins 2.5v ?
PortA may be in analog mode or in high impedence (floating) state

Quoting wdavis364 :

> Pic16F88
> Checking pin voltages Portb pins read 5vdc and Porta pins read 2.5
> vdc.
> Why is this? On another circuit somewhat similar to this, I get 5vdc
> readings on both Portb and Porta.
> Thanks
> bill
>
>
>



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I'm not sure on how to do this. My Ansel setting is 0x00. Is there another register I need to deal with?
thanks
bill
----- Original Message -----
From: Leon Heller
To: p...@yahoogroups.com
Sent: Wednesday, January 17, 2007 4:18 PM
Subject: Re: [piclist] Portb pins 5v, Porta pins 2.5v ?
----- Original Message -----
From: "wdavis364"
To:
Sent: Wednesday, January 17, 2007 9:32 PM
Subject: [piclist] Portb pins 5v, Porta pins 2.5v ?

> Pic16F88
> Checking pin voltages Portb pins read 5vdc and Porta pins read 2.5
> vdc.
> Why is this? On another circuit somewhat similar to this, I get 5vdc
> readings on both Portb and Porta.

Have you enabled them all for digital I/O, ADC pins default to analogue
inputs, not digital.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
l...@btinternet.com
http://www.geocities.com/leon_heller



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that is correct ansel should be 0 to enable porta digital.
looking at the datasheet for 16F88, shows porta has a pair of
clipping diodes tied to Vdd, Vss for each pin. that will cause the
data lines to be 2.5v or half Vdd only during high impedance state
(nether driven high or low)

to test this, set porta to output mode (trisa=0). Then set porta all
data lines high (porta=0xFF), read the voltage. Then set porta data
lines to all lows (0x00), read the voltage. Now set porta to input
mode (trisa=1). Now the data lines should be in a high impedance
state. They are floating (2.5v) because of the two clipping diodes
across each data line.

hope this helps
Daryl

At 06:48 PM 1/17/2007, you wrote:

>I'm not sure on how to do this. My Ansel setting is 0x00. Is there
>another register I need to deal with?
>thanks
>bill
>----- Original Message -----
>From: Leon Heller
>To: p...@yahoogroups.com
>Sent: Wednesday, January 17, 2007 4:18 PM
>Subject: Re: [piclist] Portb pins 5v, Porta pins 2.5v ?
>
>----- Original Message -----
>From: "wdavis364" <w...@texoma.net>
>To: <p...@yahoogroups.com>
>Sent: Wednesday, January 17, 2007 9:32 PM
>Subject: [piclist] Portb pins 5v, Porta pins 2.5v ?
>
> > Pic16F88
> > Checking pin voltages Portb pins read 5vdc and Porta pins read 2.5
> > vdc.
> > Why is this? On another circuit somewhat similar to this, I get 5vdc
> > readings on both Portb and Porta.
>
>Have you enabled them all for digital I/O, ADC pins default to analogue
>inputs, not digital.
>
>Leon
>--
>Leon Heller
>Amateur radio call-sign G1HSM
>Yaesu FT-817ND transceiver
>Suzuki SV1000S motorcycle
>l...@btinternet.com
>http://www.geocities.com/leon_heller



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--- In p...@yahoogroups.com, "Bill Davis" wrote:
>
> I'm not sure on how to do this. My Ansel setting is 0x00. Is there
another register I need to deal with?
> thanks
> bill
You may also want to check the TRISA direction control bits to ensure
that the PORTA pins are set as outputs. For all digital outputs you
would set TRISA to 0x00, and to set the pins to digital I/O you would
make ANSEL a 0x00 as well.

Good Luck,

Trent



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Well I'm getting confused here. I have already one board with inputs and outputs on bot portA and PortB and getting 5vdc readings at the pins. Now from what I understand I'm to have all pins as output on trisa if I want 5vdc?
going to need Pins RA2 and A3 as inputs.
----- Original Message -----
From: trentw_123
To: p...@yahoogroups.com
Sent: Wednesday, January 17, 2007 8:18 PM
Subject: [piclist] Re: Portb pins 5v, Porta pins 2.5v ?
--- In p...@yahoogroups.com, "Bill Davis" wrote:
>
> I'm not sure on how to do this. My Ansel setting is 0x00. Is there
another register I need to deal with?
> thanks
> bill

You may also want to check the TRISA direction control bits to ensure
that the PORTA pins are set as outputs. For all digital outputs you
would set TRISA to 0x00, and to set the pins to digital I/O you would
make ANSEL a 0x00 as well.

Good Luck,

Trent



(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

that is correct. in order to get porta pins at 5v porta needs to be
set in output mode and set to a high

if you want to use RA2, RA3 as inputs, assuming you mean digital
inputs, you would need to use a external pull-up or pull-down
resister. For some reason like to use 4.7K ohm. Doesn't really
matter what size as long as the device connected to it has enough
drive current to pull it in the opposite direction.

just a note, portB has weak internal pull-up's and portA does not.

Daryl

At 09:20 PM 1/17/2007, you wrote:

>Well I'm getting confused here. I have already one board with inputs
>and outputs on bot portA and PortB and getting 5vdc readings at the
>pins. Now from what I understand I'm to have all pins as output on
>trisa if I want 5vdc?
> going to need Pins RA2 and A3 as inputs.
>----- Original Message -----
>From: trentw_123
>To: p...@yahoogroups.com
>Sent: Wednesday, January 17, 2007 8:18 PM
>Subject: [piclist] Re: Portb pins 5v, Porta pins 2.5v ?
>
>--- In p...@yahoogroups.com,
>"Bill Davis" wrote:
> >
> > I'm not sure on how to do this. My Ansel setting is 0x00. Is there
>another register I need to deal with?
> > thanks
> > bill
>
>You may also want to check the TRISA direction control bits to ensure
>that the PORTA pins are set as outputs. For all digital outputs you
>would set TRISA to 0x00, and to set the pins to digital I/O you would
>make ANSEL a 0x00 as well.
>
>Good Luck,
>
>Trent



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Daryl, I tried what you and others suggested and my output at PortA 1 still shows 2.5. I'm using 1k resistors on all pull ups. I tried Portb pull ups without resistors and with the logic probe I only get the pos reading will go off and on(the neg does not show during switching. this only apply to PortB. It works ok with the 1k resistor with the exception to Portb 6(don't know about this). I get 5dcv reading on all i/o pins except PortA 1 which show 2.5. I'm thinking I should submit a list of all my port functions and register settings. Maybe this might help in finding the problem?
thanks
bill
----- Original Message -----
From: Daryl Berryhill
To: p...@yahoogroups.com
Sent: Thursday, January 18, 2007 7:09 AM
Subject: Re: [piclist] Re: Portb pins 5v, Porta pins 2.5v ?
that is correct. in order to get porta pins at 5v porta needs to be set in output mode and set to a high

if you want to use RA2, RA3 as inputs, assuming you mean digital inputs, you would need to use a external pull-up or pull-down resister. For some reason like to use 4.7K ohm. Doesn't really matter what size as long as the device connected to it has enough drive current to pull it in the opposite direction.

just a note, portB has weak internal pull-up's and portA does not.

Daryl

At 09:20 PM 1/17/2007, you wrote:

Well I'm getting confused here. I have already one board with inputs and outputs on bot portA and PortB and getting 5vdc readings at the pins. Now from what I understand I'm to have all pins as output on trisa if I want 5vdc?
going to need Pins RA2 and A3 as inputs.

----- Original Message -----

From: trentw_123

To: p...@yahoogroups.com

Sent: Wednesday, January 17, 2007 8:18 PM

Subject: [piclist] Re: Portb pins 5v, Porta pins 2.5v ?
--- In p...@yahoogroups.com, "Bill Davis" wrote:

>

> I'm not sure on how to do this. My Ansel setting is 0x00. Is there

another register I need to deal with?

> thanks

> bill
You may also want to check the TRISA direction control bits to ensure

that the PORTA pins are set as outputs. For all digital outputs you

would set TRISA to 0x00, and to set the pins to digital I/O you would

make ANSEL a 0x00 as well.
Good Luck,
Trent



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If there is a 1K pull-up then the voltage should either be 5V or
0V. you must have something like a voltage divider connected to
it. it would be good to know how your circuit is arranged. what is
connected to porta 1 (RA0 or RA1) ? Are those pins input / output or
analog / digital?

At 08:47 AM 1/18/2007, you wrote:

>Daryl, I tried what you and others suggested and my output at PortA
>1 still shows 2.5. I'm using 1k resistors on all pull ups. I tried
>Portb pull ups without resistors and with the logic probe I only
>get the pos reading will go off and on(the neg does not show during
>switching. this only apply to PortB. It works ok with the 1k
>resistor with the exception to Portb 6(don't know about this). I get
>5dcv reading on all i/o pins except PortA 1 which show 2.5. I'm
>thinking I should submit a list of all my port functions and
>register settings. Maybe this might help in finding the problem?
>thanks
>bill
>----- Original Message -----
>From: Daryl Berryhill
>To: p...@yahoogroups.com
>Sent: Thursday, January 18, 2007 7:09 AM
>Subject: Re: [piclist] Re: Portb pins 5v, Porta pins 2.5v ?
>
>that is correct. in order to get porta pins at 5v porta needs to be
>set in output mode and set to a high
>
>if you want to use RA2, RA3 as inputs, assuming you mean digital
>inputs, you would need to use a external pull-up or pull-down
>resister. For some reason like to use 4.7K ohm. Doesn't really
>matter what size as long as the device connected to it has enough
>drive current to pull it in the opposite direction.
>
>just a note, portB has weak internal pull-up's and portA does not.
>
>Daryl
>
>At 09:20 PM 1/17/2007, you wrote:
>
>>Well I'm getting confused here. I have already one board with
>>inputs and outputs on bot portA and PortB and getting 5vdc readings
>>at the pins. Now from what I understand I'm to have all pins as
>>output on trisa if I want 5vdc?
>> going to need Pins RA2 and A3 as inputs.
>>----- Original Message -----
>>From: trentw_123
>>To: p...@yahoogroups.com
>>Sent: Wednesday, January 17, 2007 8:18 PM
>>Subject: [piclist] Re: Portb pins 5v, Porta pins 2.5v ?
>>--- In p...@yahoogroups.com,
>>"Bill Davis" wrote:
>> >
>> > I'm not sure on how to do this. My Ansel setting is 0x00. Is there
>>another register I need to deal with?
>> > thanks
>> > bill
>>You may also want to check the TRISA direction control bits to ensure
>>that the PORTA pins are set as outputs. For all digital outputs you
>>would set TRISA to 0x00, and to set the pins to digital I/O you would
>>make ANSEL a 0x00 as well.
>>Good Luck,
>>Trent
>



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