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PIC16F877A I2C MCP23018

 
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zs6hal



Joined: 25 Feb 2021
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Location: UK

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PIC16F877A I2C MCP23018
PostPosted: Wed Mar 03, 2021 8:10 am     Reply with quote
Hi
I'm trying to use the IO expander MCP23018 using I2C from a PIC16F877A (CCS C). The issue is it works perfectly if I touch the I2C CLK wire (Using bread board). Has anyone experienced the same type of issue? Surggestions on how to resolve would be appreciated. I have tried a few small caps 100pF on the line to GND but made no diffrence.
Regards
Stan
temtronic



Joined: 01 Jul 2010
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PostPosted: Wed Mar 03, 2021 8:35 am     Reply with quote
While most will say 'white breadboards' are 'bad', I've got some 30 year old ones that work fine at 64MHz.....(still looking for a good 40pin PIC 'protoboard').
I suspect pins not being tight, possibly from too big of a jumper wire ?
You might try another area of the breadboard, or other pin locations in the 'strip of 5'.
Crazy thing is I just got a bag of premade rainbow jumpers from www.banggood.com this week, cheaper than me cutting/stripping 22ga solid wires.
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Wed Mar 03, 2021 8:58 am     Reply with quote
Also, possibly the pull-up not making a good contact.
zs6hal



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PostPosted: Thu Mar 04, 2021 1:31 pm     Reply with quote
Ttelmah wrote:
Also, possibly the pull-up not making a good contact.
Thanks
It was the pull up resistors not connected to VDD. Embarassed
temtronic



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PostPosted: Thu Mar 04, 2021 3:08 pm     Reply with quote
That's GREAT is was an 'easy' fix !!!
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Fri Mar 05, 2021 2:17 am     Reply with quote
The funny thing is that a 'human body' actually managed to give enough 'pull
up' for it to work.
I had though seen this once many years ago, which is why I raised this!. Very Happy
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