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Voltage on Reset Pin (RST)

Posted: Sun Feb 05, 2017 10:32 pm
by rjblake
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

Re: Voltage on Reset Pin (RST)

Posted: Mon Feb 06, 2017 12:05 am
by hvxl
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.

Re: Voltage on Reset Pin (RST)

Posted: Mon Feb 06, 2017 1:12 pm
by rjblake
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

Re: Voltage on Reset Pin (RST)

Posted: Mon Feb 06, 2017 7:37 pm
by rjblake
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

Re: Voltage on Reset Pin (RST)

Posted: Tue Feb 14, 2017 2:35 pm
by rjblake
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

Re: Voltage on Reset Pin (RST)

Posted: Tue Mar 14, 2017 10:16 pm
by annegerben
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?