openscope Openscope mz max input voltage on logic analyzer pins

[capablegh]

What is the max input voltage that the Openscope mz can tolerate on the logic analyzer pins. What about the GPIO pins? In the documentation I noted the Oscilloscope has +/-20V measurement range and +/-40V tolerated range (in some forum). But for the logic analyzer I see only a specific mention of 3.3V. I want to be sure before I connect the logic analyzer to either 5V (some Arduino's) devices or 12V devices (e.g. old DSC832 home security board).

Reviewing the PIC32 datasheet, and assuming I am correctly interpreting the Openscope reference manual, I can guess that the DIO[0-9] pins are 5V tolerant. Am I correct? Also, to ensure that the scope is protected I would need to not only have a voltage divider in place, but also a zener diode to ensure the voltages remain within range... what do you suggest/recommend?

[JColvin]

Hi @capablegh,

That's not quite correct; some of the pins, DIO[0-3] are 5V tolerant. The remaining pins, DIO[4-9] are not 5V tolerant. This is based on Table 4 of the PIC32MZ EF datasheet where DIO0-DIO3 (package pins B52, A64, A66, B56, respectively) are 5V tolerant, whereas the remaining 6 pins on Port E (package pins A67, A3, B2, A4, B10, A12, respectively) are not 5V tolerant. So you may use those first 4 pins for 5V tolerance, but definitely avoid putting 5V on the other pins lest the board is damaged.

As for the oscilloscope, I have not seen anything that indicates +/- 40 V tolerance on the OpenScope MZ. Can you link to the forum thread that you found that indicates this? If you are expecting to have voltage swings beyond the +/- 20V measurement range, a voltage divider and zener diode certainly would help ensure the voltages remain within the correct range. What sort of voltages are you expecting?

Thanks,
JColvin

[capablegh]

Hi @JColvin

 

Thanks for your reply.

Like you say the tech ref for Openscope MZ does not mention anything about 40V tolerance. The one reply on this forum that mentions of the 40V is here.

For some of my work with the older board (12V logic range) I will have to put the voltage divider with zener protection when connecting the LA pins. Safer to protect the investment in Openscope MZ.

[JColvin]

Hi @capablegh,

Thanks for pointing me to that thread; I'll update the OpenScope MZ reference manual with this material so that it is clear to other users as well.

Thanks,
JColvin