3.3V Microcontroller 5V Device

Dec 12, 2008 3 Replies
R

Hello...



I am using the Cortex M3 ARM Controller STM 32, And my device to be interfaced is a 5V logic which is having an SPI and needs a signal which is 1Mhz


I can make a 1Mhz signal in controller using PWM and it is having an SPI Hardware but both out put is 3.3V but the PINs of STM32 is 5V tollerable.



so the output from the device can be directly connected or with a resistor in it.


But my problem in i want to connect the following pins



STM32 DEVICE



PORT 3.3V ------------------------------> NSS1 ( 5 V ) PORT 3.3V ------------------------------> NSS2 ( 5 V ) MISO 3.3V ------------------------------> MOSI ( 5 V ) M0SI 3.3V CLCOK( 5 V ) PORT 3.3V ------------------------------> CONTROL PIN 1 ( 5 V ) PORT 3.3V ------------------------------> CONTROL PIN 1 ( 5 V ) PORT 3.3V


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H

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The Force is dark on one side, light on the other and holds the world together. Hmmm, just like Gaffer Tape then.
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L

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is cheaper at $0.17

vs.

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at $1.38

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H

If the pins on the device are TTL-compatible, you should be able to drive them directly from the 3.3 V output. 3.3 V was chosen precisely so that it could drive a 5 V TTL input (TTL has a weaker HIGH drive than LOW drive.) However, if your device *isn't* TTL-compatible (usually called something like "CMOS only") then you do need a level shifter.

-hpa

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