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For one of our projects, we are using two LS7366R ICs for interfacing with our two encoders.

Our encoders operate at 5 V and we are supplying 5 V VCC to the LS7366 chips as well. However, our control unit is a Raspberry Pi running at 3.3 V. So, what I wanted to know: is it okay if I just use the level translators and connect it to the Pi ?

Have a look at the schematic below. The idea is that both counter ICs U9 and U15 will be connected to the same MISO, MOSI and SCK signals (which are subsequently connected to level translators). The slave select signals are different though.

Encoder - LS7366 Connections:

enter image description here

LS7366 - Level Translators:

enter image description here

Can anyone confirm that the MOSI/MISO lines will not behave in any unexpected way? Is there a better way of achieving such a functionality in our design?

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Can anyone confirm that the MOSI/MISO lines will not behave in any unexpected way \$\color{red}{\text{OR}}\$ is there a better way of achieving such a functionality in our design ?

This is the \$\color{red}{\text{OR}}\$ answer...

It seems to me like you are going to a helluva lot of trouble using voltage level translators (i.e. the SN74LVC2T45D) when the LS7366R (quadrature counter devices) can work at the same logic level as your MCU (RaPi). Yes, you need to run your encoders at 5 volts but their outputs (index, A and B) can be dropped to 3.3 volt logic levels using simple resistor dividers. This then means you don't need four TI chips: -

enter image description here

Take the simple route.

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  • \$\begingroup\$ One thing... you can't run those at 30Mhz on 3.3V its out of spec, you can run them at 20Mhz (I run mine at 8Mhz). \$\endgroup\$
    – cb88
    Jan 3, 2022 at 16:54
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    \$\begingroup\$ @cb88 good catch. I shall amend my answer accordingly. \$\endgroup\$
    – Andy aka
    Jan 3, 2022 at 17:10
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    \$\begingroup\$ Nice! I just wanted to avoid anyone banging their head for missing that on the datasheet ;-) I'm using these with the DSPI library on ChipKit Lenny derived custom board... \$\endgroup\$
    – cb88
    Jan 4, 2022 at 18:21

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