Voltage on Reset Pin (RST)

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Voltage on Reset Pin (RST)

Postby rjblake » Sun Feb 05, 2017 9:32 pm

Just wanted to check and make sure regards resetting the OTGW. If I short the RST pins, gateway resets (no problem). I was looking to connect to the GPIO pin on an ESP8266 so I could reset remotely (if needed), but from what I can determine from the circuit diagram, it guess I'm looking at 5VDC on the RST. The ESP8266 GPIO is only rated at 3.3VDC, so looks like I'll need to add a level shifter to bring this back to 3.3VDC. Will this work, or end up with the OTGW stuck in a cycle of resets (will this pull it low)? Appreciate thoughts
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Re: Voltage on Reset Pin (RST)

Postby hvxl » Sun Feb 05, 2017 11:05 pm

The PIC16F88 data sheet specifies that the minimum voltage on the MCLR pin should be at least 4V for normal operation. So a regular output pin of an ESP8266 would not work.

However, according to this article, the ESP8266 I/O pins are 5V tolerant and will not clip the input to 3.3V. So, using an ESP8266 I/O pin set to Open Drain output mode should in theory work.

Disclaimer: I have not tested this and the risk is yours if you blow up anything.
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Re: Voltage on Reset Pin (RST)

Postby rjblake » Mon Feb 06, 2017 12:12 pm

hvxl wrote:The PIC16F88 data sheet specifies that the minimum voltage on the MCLR pin should be at least 4V for normal operation. So a regular output pin of an ESP8266 would not work.

However, according to this article, the ESP8266 I/O pins are 5V tolerant and will not clip the input to 3.3V. So, using an ESP8266 I/O pin set to Open Drain output mode should in theory work.

Disclaimer: I have not tested this and the risk is yours if you blow up anything.


Schelte - did further digging into this after I posted and came to the same article as well as a post from the Expressif CEO (on a Facebook group of all places) stating that the GPIO's are indeed 5V tolerant. There still remains some uncertainty as different documentation revisions seem to contradict. However...given the cost of my ESP8266, I have decided I will go ahead and try it out all the same (in the interests of science and development of mankind, obviously). Will keep others posted on status here
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Re: Voltage on Reset Pin (RST)

Postby rjblake » Mon Feb 06, 2017 6:37 pm

It is now connected up to GPIO#5 on an Adafruit Huzzah Breakout loaded with ESP-Link and didn't blow up yet. Remote reset is now fully functional and working. Will update status in a few weeks/months
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Re: Voltage on Reset Pin (RST)

Postby rjblake » Tue Feb 14, 2017 1:35 pm

rjblake wrote:It is now connected up to GPIO#5 on an Adafruit Huzzah Breakout loaded with ESP-Link and didn't blow up yet. Remote reset is now fully functional and working. Will update status in a few weeks/months

The good News is that its still going strong 1-week after hooking it up. There is not bad News to report
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Re: Voltage on Reset Pin (RST)

Postby annegerben » Tue Mar 14, 2017 9:16 pm

rjblake wrote:
rjblake wrote:It is now connected up to GPIO#5 on an Adafruit Huzzah Breakout loaded with ESP-Link and didn't blow up yet. Remote reset is now fully functional and working. Will update status in a few weeks/months

The good News is that its still going strong 1-week after hooking it up. There is not bad News to report


is the Adafruit Huzzah Breakout working? and can you tell a bit more how you perform the reset from esp-link?
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