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Attiny13 Can I use the RESET pin as I/O ?

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ItsMike

New Member
Hello,

From looking at the datasheet I see that PB5 is an I/O pin with the following alternative functions:
RESET: Reset Pin
dW:
debugWIRE I/O
ADC0:
ADC Input Channel 0
PCINT5:pin Change Interrupt, Source 5

Usually the Reset pin is connected to Vcc through a 10k resistor.

My application doesn't need a reset function, Can I just ignore it and Use it as an I/O pin ?
 

Sceadwian

Banned
Yes, however you won't be able to use in system programming anymore, once the reset line is disabled to be used as an I/O line the only way to reprogram the chip is through high voltage serial programming which requires a 12 volt signal to be placed on the reset line to enter programming mode.
 

ItsMike

New Member
Oh I see, that's too bad.

How can I multiplex the ISP signals so I could use the same pins as outputs as well ?
(These outputs will drive a Nokia 5110)
 

Sceadwian

Banned
You may not be able to. The ISP lines can't be loaded very much at all, again though this is irrelevant unless you can design your circuit so that whatever the reset line is driving can tolerate the 12 volts required to put it into programming mode, otherwise the chip will have to be removed from the system for programming.

Generally speaking if you're encountering these types of issues you need to move on to a larger chip with more I/O lines, if you still need small space then you need to learn how to work with surface mount components. There are MLF components with dozens of I/O lines that are smaller than 8pin DIPS. You need to make sure you're using the right device for the task, you'll spend more time effort and energy and possibly fail to adapt the device you're currently using to your needs.
 
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