December 10, 2023, 10:33:56 PM

AVR-ISP-MKII with 3.3V Target?

Started by iiimjags, November 21, 2016, 04:14:27 PM

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I need to use the AVR-ISP-MKII with an ATMega 328P target operating at 3.3V.

I understand how to set the jumpers on the AVR-ISP-MKII. I have them configured for 3.3V and to NOT supply power to the target.  This works fine.

However, I am concerned because the AVR-ISP-MKII schematic indicates the AVR inside the AVR-ISP-MKII operates at 5V regardless of the jumper settings.  As a result, it seems that the target will receive 5V signals from the AVR-ISP-MKII, which would violate the input voltage restrictions on the 3.3V 328P target.

Please -- can the  AVR-ISP-MKII *safely* be connected to a 3.3V target?  There do not seem to be level shifters within the AVR-ISP-MKII and so I do not see how it is possible to safely connect to a 3.3V target.

Thank you!


Do not worry, it is safe to use AVR-ISP-MK2 with 3.3V targets. Inspect the schematic - the resistor matrices and the BAT54C Schottky barrier diodes take care of the voltage difference.

We have provided the option to power the chip by 3.3V but it is not recommended to use this option since this would limit the use of the unit with 5V targets and also it requires opening the unit and chaning the positon of an SMT jumper. In the schematic the jumper is named "MCU_5V/3.3V". Opening the box and mofiying the jumper also voids the warrnty.

Best regards,
Technical support and documentation manager at Olimex