4.5.2 Operation at Other Voltages

The ATtiny817 Xplained Pro board is by default operated at 3.3V, but it also has the possibility of running at other voltages from an external supply. The EDBG is designed to run from a 3.3V supply and won't work with other voltages, therefore all connections from the EDBG and the on-board 3.3V regulator to the ATtiny817 should be removed.

To completely disconnect the EDBG and the on-board power supply from the ATtiny817, do the following:

  • Remove the two jumpers from the on-board 3-pin current measurement headers (J101 and J102), and connect the two center pins (pin 2) with a wire or an ammeter, as shown in Figure 4-7
  • Remove R404, R406, R407, R408, R414, R415, R416, R417, R420, R425, and R426
  • Optionally, cut J100 to remove power to the on-board current measurement headers (J101 and J102) from the on-board regulator

Figure 4-6 shows all components that have to be removed from the bottom side of the PCB for operation at other voltages. To locate the other components, see the assembly drawing in the section above. When the components are removed, the kit can be supplied with the desired voltage through the pins marked 3.3V (pin four) and GND (pin two) on the Xplained Pro power header. To program and debug the ATtiny817, the 2x5 50 mil UPDI debug connector has to be used with an external debugger.

Info: Operating the ATtiny817 with other voltages than 3.3V requires physical modifications on the kit using a soldering iron and an external debugger for programming the ATtiny817. The on-board current measurement works only at 3.3V. The on-board LED is selected for 3.3V operation. The light level at 1.8V operation is very low. To increase the emitted light level, the value of the series resistor can be lowered. The EDBG functionality can be restored by re-soldering the removed components. If J100 is cut, a 0Ω resistor can be soldered across the cut.
CAUTION: The voltage supplied through the power header is applied directly to the ATtiny817 and the extension headers. Applying a voltage higher than 5.5V may damage the board permanently.
Figure 4-6. ATtiny817 Xplained Pro EDBG Disconnect
Figure 4-7. ATtiny817 Xplained Pro Current Measurement Headers