ESP32 GPIO Input Hysteresis (Schmitt Trigger)?

ycroosh
Posts: 2
Joined: Mon Dec 28, 2020 7:07 am

ESP32 GPIO Input Hysteresis (Schmitt Trigger)?

Postby ycroosh » Mon Dec 28, 2020 7:11 am

Hello,
I can't find any info on whether or not ESP32-WROOM-32E has Schmitt triggers on GPIO inputs and what (if any) the hysteresis is.
Any info would be appreciated.
Thank you
Yuriy

ESP_Sprite
Posts: 4396
Joined: Thu Nov 26, 2015 4:08 am

Re: ESP32 GPIO Input Hysteresis (Schmitt Trigger)?

Postby ESP_Sprite » Tue Dec 29, 2020 1:33 am

They do not.

PeterR
Posts: 593
Joined: Mon Jun 04, 2018 2:47 pm

Re: ESP32 GPIO Input Hysteresis (Schmitt Trigger)?

Postby PeterR » Tue Dec 29, 2020 10:29 pm

You should really describe your original problem along with question.
No schmitt but a software latch, counter, RMT might work just as well (depending on you're actual problem).
& I also believe that IDF CAN should be fixed.

ycroosh
Posts: 2
Joined: Mon Dec 28, 2020 7:07 am

Re: ESP32 GPIO Input Hysteresis (Schmitt Trigger)?

Postby ycroosh » Wed Dec 30, 2020 7:07 pm

PeterR,
I need to read four to six external sensors that communicate using a two-wire protocol (somewhat similar to SPI). The sensort provide 32 clock pulses on the "Clock" line, and the data is read on the falling edge. The refresh rate is about 20-100 Hz per sensor (20Hz when they are idle, 100Hz when the values are changing rapidly), and clock frequency is about 25KHz. I don't have any control over the sensors, so they can send their data a any random time.
Thank you
Yuriy

PeterR
Posts: 593
Joined: Mon Jun 04, 2018 2:47 pm

Re: ESP32 GPIO Input Hysteresis (Schmitt Trigger)?

Postby PeterR » Thu Dec 31, 2020 11:32 pm

Not tried TWI on ESP before.
SPI should do it. You can figure the mode. Some edge cases on hard wiring CS to figure but doable.
Trouble is you have 4-6 asynchronous sources & you do not have 6 SPI devices on the ESP.
25MHz is also probably too fast if you use the ESP GPIO mux (use non native SPI pins).


Tricky problem. I would look (maybe) at port extenders (with FIFOs) and hook one or two to the ESP, like a SPI 4:1 multiplexor.
Whats the data source?

If UPC cost (rather than NRE) really is your thing then you might be able to reach 4 or so devices using ESP alone e.g. a combination of SPI and RMT etc. The 25MHz will be interesting though because of the GPIO mux clock delay limitations.
Obviously you need hardware support at 25Mhz.

Gut reaction is that you need external circuits.
& I also believe that IDF CAN should be fixed.

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