Set the pot for a voltage ABOVE 2.1 V, (if the pot is across Vcc & GND, what is the chance it will reach 11 V ?) Plug the jumper with 2.1 V on it into the RESET pin and remove it quickly. Put a pot across Vcc & GND and connect the wiper to a breadboard and connect a DMM on Volts and a jumper to the wiper. His question was what voltage level will trigger a RESET on a MEGA2560. As I stated to the OP, his question was NOT what does it say or not say on the data sheet. I have an UNO ,not a Mega, so all my testing was done with a 328. Also, I know what the logic levels are stated in the datasheet. Technically, you are correct, I should have clarified that but I think it is irrelevant in the OP's case. and become more familiar with actual Low and High input pin levels both regular and Schmitt trigger type right about I should have specified a limit of Vcc, instead of just saying above, but really, do you think the OP interpreted it any other way ? (meaning, do you think he understood me to be saying anything other than 'above x voltage with a max of Vcc?). Commonly used to fix accidently Bricked controllers.

Pull up the reset pin above ~ 11V (read the data sheet.) and you will place the chip in HV programming mode. In the middle of Raschemmel your information is not quite correct. But if HIGH output will be applied directly to RESET (something between 2,8-3,3V) it is not enough to keep mega surely out of reset even if it has reset pin pulled up to Vcc. LOW from XBee (max 0.5V isn't it ?) will be LOW for mega also. 'Min' means the lowest value where the pin is guaranteed to be read as high.'Max' means the highest value where the pin is guaranteed to be read as low.If you see DC characteristics (table 31.1) it is 0.1Vcc for LOW (max 0.5V at Vcc= 5V ) ! And look at notes below the table: If Vcc = 5V, it means between GND and 1.0V. Max 0.2Vcc has to be on RESET pin to surely caused MCU reset. If Vcc = 5V, it means between 4,5V and Vcc. Min 0.9Vcc has to be on RESET pin to surely prevent MCU of reset. You have to agree with that conclusion, right? Sorry for it and don't beat the table means that when the xbee outputs a logoc LOW, as long as it is less than the 0.9 V Max then the Mega will still see it as a LOW and execute a Reset. I had corrected some mixture of V and V CC. I realised that I was not so thoroughgoing as I read this thread today.

Long story short, the xbee can reset the UNO no problem because it can pull the RESET pin below 2.0 V, and when it raises the RESET pin back to a HIGH, the UNO will reset.Ĭorrection, when the voltage drops below the 2.0V threshold, the processor halts, but doesn't execute the RESET sequence until the rising edge of the HIGH following the low, so technically SOMETHING does happen, or to be more accurate, EVERYTHING STOPS HAPPENING and just waits until the voltage returns to a HIGH.Īt the first. The question was not exactly correct but you are not expected to know that nothing happens until the RESET pin goes HIGH. You asked what voltage, when applied to the RESET pin will I know what the datasheet says but you that is not what you asked. If you're sceptical, take a jumper and plug it directly to GROUND and plug it into the RESET pin and leave it. The sequence is LOW (less than 2.0V), HIGH=>RESET. It is executed when the reset pin is pulled BELOW the lower threshold voltage of a LOGIC HIGH and THEN RAISED back up to a logic HIGH. Obviously, this means that RESET is NOT executed when the RESET pin is pulled LOW. If, however, the wiper voltage is or LESS THAN 2.05 V (+/- 50mV), when you plug the jumper into the RESET pin, nothing will happen UNTIL you REMOVE it. You will find that as long as the voltage on the RESET pin remains ABOVE 2.1 V (+/- 50 mV), you can plug the jumper into the RESET pin and remove it and nothing happens. Now connect a pot across the 5V bus (or 3.3V, it really isn't going to matter either way) and connect the wiper of the pot to the jumper you connected to the RESET pin. Now, if you want to find out the answer to your question, forget what you readĪnd put a jumper from the RESET(NOT) pin to a breadboard. 0.1Vcc or lower is required to reset, correct? 0.9Vcc or more is required to come out of reset, correct? I am still confused with what threshold means here.

Arduino mega 2560 digital pin voltage