Hello everyone, I have 2 questions related to using a NANO as an ISP (title hints).
What I'm doing?
Basically building myself a programmer to program and burn bootloaders to ATMega328P-PU chips. I have mostly followed all these pages:
- https://docs.arduino.cc/retired/hacking/hardware/building-an-arduino-on-a-breadboard/
- https://docs.arduino.cc/built-in-examples/arduino-isp/ArduinoToBreadboard/
- https://support.arduino.cc/hc/en-us/articles/4841602539164-Burn-the-bootloader-on-UNO-Mega-and-classic-Nano-using-another-Arduino
- https://docs.arduino.cc/built-in-examples/arduino-isp/ArduinoISP/
It works as expected, successfully uploaded a blink sketch to a breadboard ATMega.
Here's what I'm wondering:
10uF Reset capacitor
From what I read among the pages above, is that this capacitor should be used in the board with the ISP sketch, that has a sepparate USB interface for PC communication. Is this really required for the NANO too? I'm unsure if NANO has that extra controller. Seen an ATMega16U2 chip on UNOs which I believe is for the USB stuff. Related to this, would this prevent accidental sketch upload to the ISP board?
Additional diodes in MISO, MOSI and SCK lines
I was thinking I could throw in some diodes into these lines to prevent reverse voltages coming from the target ATMega chip on these lines, since after all, they are managable digital pins. I had a weird situation where I uploaded the blink sketch to target to blink pin 13, and when done, the NANO red LED was blinking instead xD pin 13 is also SCK, so I'm guessing somehow, the target ATMega was blinking the NANO's LED, although quite dimly.
Adding diodes to those lines would make a 0.7V drop, from the roughly 4.6V I get from the NANO connected via USB. Would that screw things up when doing communication?
That is all.
Thanks in advance.
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