What can be behavior for 3.3v PIC and 5v display

Hi,
I am using one display works on 5 volt and interface is UART. And PIC16F886 runs on 3.3volt. what is the behavior if we interface both on uart.

When i connect display to the controller and controller stops working. do i need to use voltage translator for 3.3V and 5V.

Re: what can be behavior for 3.3v PIC and 5v display

Hi,

Take both datasheets.
You need to check valid signal levels: look for Vol, Voh, Vil, Vih.
Then check for absolute input levels. Especially if the 3V3 device can handle 5V inputs.

Klaus

Re: what can be behavior for 3.3v PIC and 5v display

The PIC16F886 offers a wide operating voltage range of 2.0V to 5.5V.

Why not increase the voltage supply of the PIC16F886 to 5.0V and eliminate the problem?

If that is not possible, you might find the attached Microchip TipsNTricks Guide of interest.

BigDog

Re: what can be behavior for 3.3v PIC and 5v display

yes i have connected other sensor there which works on 3v3.
In both way i will have to use voltage translator.

Re: what can be behavior for 3.3v PIC and 5v display

Some kind of voltage translation will be needed.
1. uC inputs must not be driven above 3.3 V.
2. Display may need logic high level above 3.3V, review specification.

Re: what can be behavior for 3.3v PIC and 5v display

There is a trick worth mentioning but it may not be applicable to that particular PIC:

On devices with 5V tolerant pins, even if running from a 3.3V supply, if the LCD lines are pulled up to 5V using resistors and the PIC ports are driven low, the TRIS registers can be used to safely control the data output. If a pin is set to input mode, the external pull-up will lift it to 5V, if set to output mode, the driver will pull it down to 0V.

Brian.

Re: what can be behavior for 3.3v PIC and 5v display

Thanks. I will try using pull up's first.

But is this stuck behavior is expected after connecting 5v peripheral to mcu works 3v3?

Re: what can be behavior for 3.3v PIC and 5v display

But is this stuck behavior is expected after connecting 5v peripheral to mcu works 3v3?

Click to expand...

No PIC16 or PIC18 operated at 3.3V is 5V tolerant as far as I'm aware of, PIC16F886 surely isn't. It's not acceptable to drive a higher input voltage than VDD to any IO pin, at least not without limiting the clamp current respectively. You would know if you had read the datasheet thoroughly.

It might be sufficient to place a series resistor of several kOhm between 5V logic output and PIC input.

I don't know what happens specifically in your design, we would need to look at the circuit details.

Re: what can be behavior for 3.3v PIC and 5v display

Hi,
I am using RX and TX to connect display and mlx sensor is on i2c. Here is attached schematic.

Re: what can be behavior for 3.3v PIC and 5v display

Hi,

Tx and Rx sounds like UART....but you talk about I2C.
How does this meet?

Klaus

Re: what can be behavior for 3.3v PIC and 5v display

No. I was talking about uart only by saying TX and RX.

Hi,
I am using one display works on 5 volt and interface is UART. And PIC16F886 runs on 3.3volt. what is the behavior if we interface both on uart.

When i connect display to the controller and controller stops working. do i need to use voltage translator for 3.3V and 5V.

Click to expand...

i have connected other sensor(MLX temp sensor) on i2c which also works on 3v3. Sensor is working fine for me.

Re: what can be behavior for 3.3v PIC and 5v display

Till now you have not read the datasheet of the display ?

Hi ep.hobbyiest

Assuming you are talking about uart.

Your question comes as a doubt to million of embedded engineers

The uart module of your controller is 5V tolerant.
It will work well and will not be affected with a 5V logic.
But the intention of you driving the microcontroller in 3.3V will be power saving I guess.

Also controllers may have a strong pull-up Resistors at uart lines. So if you connect a 5V logic it may create potential imbalance. Even though you will have any problem, it is not highly reliable.

Then now, the solution.

Actually you don't want to use any voltage translators
U can use a voltage dividing Resistors from the TX line of the display to the Rx of microcontroller.
And you can directly connect the TX of microcontroller to the Rx of display. Make sure that the display have a VIH value below 3.3V. Mostly it will, so don't worry.

Just go and rock!!!!!!

Congrats!!!!