Weak internal pull up
- Thread starter Protolisk
- Start date
BeanieBots
Moderator
None of the PICAXE have weak pull-ups enabled.
However, if the PIC supports weak pull-up, then you can poke the required register to set the pull-ups.
Don't know specifically about the 12F683, you'll have to check the datasheet.
However, if the PIC supports weak pull-up, then you can poke the required register to set the pull-ups.
Don't know specifically about the 12F683, you'll have to check the datasheet.
westaust55
Moderator
Weak Pull-up control for 08M
Have a look at my variable map covering most current PICAXE's. Post 14 in this thread:
http://www.picaxeforum.co.uk/showthread.php?t=9525&page=2
You need to poke the SFR's (See bottom left of the sheet).
Two registers involved:
1. The Options register at POKE location 129.
Bit 7 must be a zero to enable WPU's in general
2. The Weak Pull-Up register at POKE location 149
Setting the desired bit correspnding to an IO to a "1" turns on the WPU.
You should also have a read of the datasheet for the PIC12F683.
You may need to PEEK the Option Register to get the current value then use that value to just turn on bit 7 and POKE the value back.
Have a look at my variable map covering most current PICAXE's. Post 14 in this thread:
http://www.picaxeforum.co.uk/showthread.php?t=9525&page=2
You need to poke the SFR's (See bottom left of the sheet).
Two registers involved:
1. The Options register at POKE location 129.
Bit 7 must be a zero to enable WPU's in general
2. The Weak Pull-Up register at POKE location 149
Setting the desired bit correspnding to an IO to a "1" turns on the WPU.
You should also have a read of the datasheet for the PIC12F683.
You may need to PEEK the Option Register to get the current value then use that value to just turn on bit 7 and POKE the value back.
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Oh, I wasn't saying don't do it, but check out the PIC Data sheet to see power consumption for weak pullups.
In a recent thing I did with a 16F886 I had to revert to external 1M5 pullups to get my power down. They may be called weak, but a current consumption of 250uA (ish) is quite steep for a low power circuit that could easily work at a tenth of that (average).
In a recent thing I did with a 16F886 I had to revert to external 1M5 pullups to get my power down. They may be called weak, but a current consumption of 250uA (ish) is quite steep for a low power circuit that could easily work at a tenth of that (average).
Here are the pages from the Data Sheet.
Have a look and you'll understand Westaust's notes.
Note: Westy talks in decimal, the Data Sheet in hex.
So, by Poking you tell the PIC;
1) I want you to use Weak Pullups (Option s Reg)
2) These are the pins i want you to pullup 'weakly'.
Note2: On I/O pins if you change the I/O direction you will have to reinstate WPUs if you need them again.
Have a look and you'll understand Westaust's notes.
Note: Westy talks in decimal, the Data Sheet in hex.
So, by Poking you tell the PIC;
1) I want you to use Weak Pullups (Option s Reg)
2) These are the pins i want you to pullup 'weakly'.
Note2: On I/O pins if you change the I/O direction you will have to reinstate WPUs if you need them again.
