MCP23017: inverted output relay mode is shortly toggeling the outputs to on during boot/init phase #21400
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Eisbahn
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forget the idea with pullup... As the MCP is very likely going in init phase to drive its GPIO to low, a high ohm pull-up won't help at all and would be overruled by the GPIO state. Think I have to switch off the SSR behind it, e.g. depowering them for the first 3sec after supply power is back |
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Dear all,
having three MCP23017 connected to my ESP, acting as 24 outputs and 24 inputs. The outputs are configured as inverted relay (meaning I do have active low output logic), the inputs as buttons:
{"NAME":"MCP23017","BASE":0,"GPIO":[256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,272,273,274,275,276,277,278,279,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55]}
That worked perfectly, until today... Due to an interrupt of power from my local EVU/power company, I had a short power interruption of my whole hardware setup. After power was right back, my PSU showed a melted fuse :-)
What happens always: during initial phase, all output pins are shortly (for 1...2sec or so) turned on (=having GND potential on GPIO line) and afterwards off (having VCC on the GPIOs). Better: after shortly being turned on, they're changing to their last state. Sadly turning on all outputs for a short time draws lots of current in my setup, not funny...
Is there any way to prevent this from SW side? What would be a good HW solution?
Otherwise I would use external 68k pullups on each pin.
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