Does ATtiny RESET pin need a resistor?
$begingroup$
I need to make sure that my ATtiny does not reset unexpectedly. To do that, I am planning on connecting the RESET pin directly to VCC.
However, I have heard some places that you need a 10k resistor between VCC and the RESET pin, to prevent too much current from flowing into the RESET pin and burning the IC. I have also seen some places that you do not need a resistor between VCC and RESET, and I have also read a few places that you do not even need to connect RESET to anything, because it is pulled high internally.
I could not find any definitive answer on this, and I would like to know what the case would be for each of these condidions (directly to VCC, VCC through resistor, don't connect RESET pin at all) is.
microcontroller digital-logic resistors attiny attiny85
$endgroup$
add a comment |
$begingroup$
I need to make sure that my ATtiny does not reset unexpectedly. To do that, I am planning on connecting the RESET pin directly to VCC.
However, I have heard some places that you need a 10k resistor between VCC and the RESET pin, to prevent too much current from flowing into the RESET pin and burning the IC. I have also seen some places that you do not need a resistor between VCC and RESET, and I have also read a few places that you do not even need to connect RESET to anything, because it is pulled high internally.
I could not find any definitive answer on this, and I would like to know what the case would be for each of these condidions (directly to VCC, VCC through resistor, don't connect RESET pin at all) is.
microcontroller digital-logic resistors attiny attiny85
$endgroup$
$begingroup$
How will you program your attiny if the reset is always high?
$endgroup$
– BeB00
3 hours ago
$begingroup$
when in doubt, use a 10kΩ resistor ..... that way you have a known state at the reset pin and you can pull it low if you have to for programming ..... direct connection to Vcc would prevent programming
$endgroup$
– jsotola
3 hours ago
add a comment |
$begingroup$
I need to make sure that my ATtiny does not reset unexpectedly. To do that, I am planning on connecting the RESET pin directly to VCC.
However, I have heard some places that you need a 10k resistor between VCC and the RESET pin, to prevent too much current from flowing into the RESET pin and burning the IC. I have also seen some places that you do not need a resistor between VCC and RESET, and I have also read a few places that you do not even need to connect RESET to anything, because it is pulled high internally.
I could not find any definitive answer on this, and I would like to know what the case would be for each of these condidions (directly to VCC, VCC through resistor, don't connect RESET pin at all) is.
microcontroller digital-logic resistors attiny attiny85
$endgroup$
I need to make sure that my ATtiny does not reset unexpectedly. To do that, I am planning on connecting the RESET pin directly to VCC.
However, I have heard some places that you need a 10k resistor between VCC and the RESET pin, to prevent too much current from flowing into the RESET pin and burning the IC. I have also seen some places that you do not need a resistor between VCC and RESET, and I have also read a few places that you do not even need to connect RESET to anything, because it is pulled high internally.
I could not find any definitive answer on this, and I would like to know what the case would be for each of these condidions (directly to VCC, VCC through resistor, don't connect RESET pin at all) is.
microcontroller digital-logic resistors attiny attiny85
microcontroller digital-logic resistors attiny attiny85
asked 3 hours ago
eezeeeze
59110
59110
$begingroup$
How will you program your attiny if the reset is always high?
$endgroup$
– BeB00
3 hours ago
$begingroup$
when in doubt, use a 10kΩ resistor ..... that way you have a known state at the reset pin and you can pull it low if you have to for programming ..... direct connection to Vcc would prevent programming
$endgroup$
– jsotola
3 hours ago
add a comment |
$begingroup$
How will you program your attiny if the reset is always high?
$endgroup$
– BeB00
3 hours ago
$begingroup$
when in doubt, use a 10kΩ resistor ..... that way you have a known state at the reset pin and you can pull it low if you have to for programming ..... direct connection to Vcc would prevent programming
$endgroup$
– jsotola
3 hours ago
$begingroup$
How will you program your attiny if the reset is always high?
$endgroup$
– BeB00
3 hours ago
$begingroup$
How will you program your attiny if the reset is always high?
$endgroup$
– BeB00
3 hours ago
$begingroup$
when in doubt, use a 10kΩ resistor ..... that way you have a known state at the reset pin and you can pull it low if you have to for programming ..... direct connection to Vcc would prevent programming
$endgroup$
– jsotola
3 hours ago
$begingroup$
when in doubt, use a 10kΩ resistor ..... that way you have a known state at the reset pin and you can pull it low if you have to for programming ..... direct connection to Vcc would prevent programming
$endgroup$
– jsotola
3 hours ago
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
I don't think theres a technical reason why you couldn't connect your reset pin directly to +V, as long as it was already programmed and you never wanted to modify that program. As far as I'm aware, there is no function of the attiny that requires the reset pin to be pulled low (for example, the watchdog timer doesn't try to pull the reset line low).
Having said that, there isn't really a good reason why you would want to have the line directly connected, and there are quite a few where you wouldn't want it to be directly connected (like programming, and manual reset etc).
The attiny does have an internal pull-up to VCC, but its quite weak (~100k iirc), so environmental conditions could cause a spontaneous reset. If you're worried about this, you should use an external pull-up resistor. It means using an extra component, but it's safer, especially if your reset pin is routed to a programming connector.
$endgroup$
add a comment |
$begingroup$
The reset pin is internally pulled-up and glitch filtered so you do not need a resistor.
You can leave the pin unconnected (no trace since a trace can pick up noise) and it would take some pretty strong noise to make the chip reset unexpectedly - probably enough that other bad things would happen first.
If you really never want the chip to get reset then you can set the RSTDISBL
(reset disable) fuse after programming your firmware. Once this fuse is set, the reset pin becomes an IO pin and will not reset the chip even if tied to ground.
Note that after disabling the reset pin with RSRDISBL
it is either harder or impossible to reprogram the chip depending on which ATTINY you are using.
$endgroup$
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
add a comment |
$begingroup$
First, in the ATtiny25/45/85 datasheet, page 161, it suggested that there's a internal pull-up resistor between 30 kΩ - 60 kΩ on the RESET pin. It means the MCU will almost always work for a hobby project. However, if the requirement is high reliability,
I need to make sure that my ATtiny does not reset unexpectedly.
Then you have to put external EMI/RFI into your consideration. I strongly suggest reading AVR040: EMC Design Considerations.
New contributor
$endgroup$
add a comment |
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3 Answers
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active
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votes
3 Answers
3
active
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$begingroup$
I don't think theres a technical reason why you couldn't connect your reset pin directly to +V, as long as it was already programmed and you never wanted to modify that program. As far as I'm aware, there is no function of the attiny that requires the reset pin to be pulled low (for example, the watchdog timer doesn't try to pull the reset line low).
Having said that, there isn't really a good reason why you would want to have the line directly connected, and there are quite a few where you wouldn't want it to be directly connected (like programming, and manual reset etc).
The attiny does have an internal pull-up to VCC, but its quite weak (~100k iirc), so environmental conditions could cause a spontaneous reset. If you're worried about this, you should use an external pull-up resistor. It means using an extra component, but it's safer, especially if your reset pin is routed to a programming connector.
$endgroup$
add a comment |
$begingroup$
I don't think theres a technical reason why you couldn't connect your reset pin directly to +V, as long as it was already programmed and you never wanted to modify that program. As far as I'm aware, there is no function of the attiny that requires the reset pin to be pulled low (for example, the watchdog timer doesn't try to pull the reset line low).
Having said that, there isn't really a good reason why you would want to have the line directly connected, and there are quite a few where you wouldn't want it to be directly connected (like programming, and manual reset etc).
The attiny does have an internal pull-up to VCC, but its quite weak (~100k iirc), so environmental conditions could cause a spontaneous reset. If you're worried about this, you should use an external pull-up resistor. It means using an extra component, but it's safer, especially if your reset pin is routed to a programming connector.
$endgroup$
add a comment |
$begingroup$
I don't think theres a technical reason why you couldn't connect your reset pin directly to +V, as long as it was already programmed and you never wanted to modify that program. As far as I'm aware, there is no function of the attiny that requires the reset pin to be pulled low (for example, the watchdog timer doesn't try to pull the reset line low).
Having said that, there isn't really a good reason why you would want to have the line directly connected, and there are quite a few where you wouldn't want it to be directly connected (like programming, and manual reset etc).
The attiny does have an internal pull-up to VCC, but its quite weak (~100k iirc), so environmental conditions could cause a spontaneous reset. If you're worried about this, you should use an external pull-up resistor. It means using an extra component, but it's safer, especially if your reset pin is routed to a programming connector.
$endgroup$
I don't think theres a technical reason why you couldn't connect your reset pin directly to +V, as long as it was already programmed and you never wanted to modify that program. As far as I'm aware, there is no function of the attiny that requires the reset pin to be pulled low (for example, the watchdog timer doesn't try to pull the reset line low).
Having said that, there isn't really a good reason why you would want to have the line directly connected, and there are quite a few where you wouldn't want it to be directly connected (like programming, and manual reset etc).
The attiny does have an internal pull-up to VCC, but its quite weak (~100k iirc), so environmental conditions could cause a spontaneous reset. If you're worried about this, you should use an external pull-up resistor. It means using an extra component, but it's safer, especially if your reset pin is routed to a programming connector.
answered 3 hours ago
BeB00BeB00
2,932722
2,932722
add a comment |
add a comment |
$begingroup$
The reset pin is internally pulled-up and glitch filtered so you do not need a resistor.
You can leave the pin unconnected (no trace since a trace can pick up noise) and it would take some pretty strong noise to make the chip reset unexpectedly - probably enough that other bad things would happen first.
If you really never want the chip to get reset then you can set the RSTDISBL
(reset disable) fuse after programming your firmware. Once this fuse is set, the reset pin becomes an IO pin and will not reset the chip even if tied to ground.
Note that after disabling the reset pin with RSRDISBL
it is either harder or impossible to reprogram the chip depending on which ATTINY you are using.
$endgroup$
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
add a comment |
$begingroup$
The reset pin is internally pulled-up and glitch filtered so you do not need a resistor.
You can leave the pin unconnected (no trace since a trace can pick up noise) and it would take some pretty strong noise to make the chip reset unexpectedly - probably enough that other bad things would happen first.
If you really never want the chip to get reset then you can set the RSTDISBL
(reset disable) fuse after programming your firmware. Once this fuse is set, the reset pin becomes an IO pin and will not reset the chip even if tied to ground.
Note that after disabling the reset pin with RSRDISBL
it is either harder or impossible to reprogram the chip depending on which ATTINY you are using.
$endgroup$
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
add a comment |
$begingroup$
The reset pin is internally pulled-up and glitch filtered so you do not need a resistor.
You can leave the pin unconnected (no trace since a trace can pick up noise) and it would take some pretty strong noise to make the chip reset unexpectedly - probably enough that other bad things would happen first.
If you really never want the chip to get reset then you can set the RSTDISBL
(reset disable) fuse after programming your firmware. Once this fuse is set, the reset pin becomes an IO pin and will not reset the chip even if tied to ground.
Note that after disabling the reset pin with RSRDISBL
it is either harder or impossible to reprogram the chip depending on which ATTINY you are using.
$endgroup$
The reset pin is internally pulled-up and glitch filtered so you do not need a resistor.
You can leave the pin unconnected (no trace since a trace can pick up noise) and it would take some pretty strong noise to make the chip reset unexpectedly - probably enough that other bad things would happen first.
If you really never want the chip to get reset then you can set the RSTDISBL
(reset disable) fuse after programming your firmware. Once this fuse is set, the reset pin becomes an IO pin and will not reset the chip even if tied to ground.
Note that after disabling the reset pin with RSRDISBL
it is either harder or impossible to reprogram the chip depending on which ATTINY you are using.
edited 2 hours ago
answered 3 hours ago
bigjoshbigjosh
7,1351736
7,1351736
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
add a comment |
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
To be fair, Atmel (Microchip) does recommend an external reset pull-up in noisy environments, per AVR042, suggesting that it's not an extremely rare event
$endgroup$
– BeB00
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
@beb00 Yea, that note also sort of maybe suggests attaching a capacitor between RESET and ground which doesn't make much sense. In practice, an extra pull-up might help if there is a long trace that connected to the RESET pin, but if the pin in connected then there is really very very little length there to pick up an e field and the glitch detector should block any inductively coupled impulses. I've never seen an ATTINY spontaneously reset due to noise on an unconnected RESET. Have you?
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
$begingroup$
Note that I have seen ATTINYs spontaneously reset from a negative ESD strike directly to the Vcc line, but this is due to under voltage and not the reset line.
$endgroup$
– bigjosh
2 hours ago
add a comment |
$begingroup$
First, in the ATtiny25/45/85 datasheet, page 161, it suggested that there's a internal pull-up resistor between 30 kΩ - 60 kΩ on the RESET pin. It means the MCU will almost always work for a hobby project. However, if the requirement is high reliability,
I need to make sure that my ATtiny does not reset unexpectedly.
Then you have to put external EMI/RFI into your consideration. I strongly suggest reading AVR040: EMC Design Considerations.
New contributor
$endgroup$
add a comment |
$begingroup$
First, in the ATtiny25/45/85 datasheet, page 161, it suggested that there's a internal pull-up resistor between 30 kΩ - 60 kΩ on the RESET pin. It means the MCU will almost always work for a hobby project. However, if the requirement is high reliability,
I need to make sure that my ATtiny does not reset unexpectedly.
Then you have to put external EMI/RFI into your consideration. I strongly suggest reading AVR040: EMC Design Considerations.
New contributor
$endgroup$
add a comment |
$begingroup$
First, in the ATtiny25/45/85 datasheet, page 161, it suggested that there's a internal pull-up resistor between 30 kΩ - 60 kΩ on the RESET pin. It means the MCU will almost always work for a hobby project. However, if the requirement is high reliability,
I need to make sure that my ATtiny does not reset unexpectedly.
Then you have to put external EMI/RFI into your consideration. I strongly suggest reading AVR040: EMC Design Considerations.
New contributor
$endgroup$
First, in the ATtiny25/45/85 datasheet, page 161, it suggested that there's a internal pull-up resistor between 30 kΩ - 60 kΩ on the RESET pin. It means the MCU will almost always work for a hobby project. However, if the requirement is high reliability,
I need to make sure that my ATtiny does not reset unexpectedly.
Then you have to put external EMI/RFI into your consideration. I strongly suggest reading AVR040: EMC Design Considerations.
New contributor
New contributor
answered 20 mins ago
比尔盖子比尔盖子
1011
1011
New contributor
New contributor
add a comment |
add a comment |
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$begingroup$
How will you program your attiny if the reset is always high?
$endgroup$
– BeB00
3 hours ago
$begingroup$
when in doubt, use a 10kΩ resistor ..... that way you have a known state at the reset pin and you can pull it low if you have to for programming ..... direct connection to Vcc would prevent programming
$endgroup$
– jsotola
3 hours ago