Flash chips running with 3.3v and have 5v input tolerance

[longpole001]

hI GUYS ,

I have a pic running at 5v , have SPI BUS with level converters to 3.3v , but now looking at adding a flash chip to the spi bus
and i prefer not to ad more level converters for the ce/hold/wp inputs if i can avoid

wondering if anyone has a solution for using a FLASH chip running at 3.3v , where the inputs for CE , hold , WP are 5v input tolerant


most Flash chips i have found have internal pullups on these pins as well

i prefer to do a flash for the size/ speed relative to eeprom , but most eeprom can run at 5v


regards

sheldon

[longpole001]

well no such animal that i can find all are 3.3v and are not 5v input tolerant

[Archangel]

Hi Sheldon,
I will start off by saying, I do not know how those flash chips work. Here is my thoughts: If your pic is switching between ground and open collector, it should be as simple as powering the flash chip from a voltage divider, 3.3k down, 2.2k up should do it. Now if it (PIC) drives high then it will not work.

[EarlyBird2]

This has set me thinking.

I initial thought why not have two chips and use one to handle the Human Machine Interface (HMI).
This morphed into why not use a PC as the HMI which then became use a Smart Phone with Bluetooth connection running an App.

Too many ideas? I have to be careful as I have been warned about getting too excited!

[longpole001]

well after many a search , i did not find any flash that allowed for 5v tolerant inputs ,
i have interfaced the 8mb flash via level converter 75LVX125 for the CE pin for the moment , have tied high the W and Hold lines high and when data is complete for the menus/fonts etc , with software protect those sectors which are used from further writing.

the PCB has been designed to support the SD and adding a flash chip is a pain but not one that is hard to do. for an extra CE required
resistor divider may do as well , but ill test after it working for add on board when done.

what i have found is some of the flash chips support duel / quad spi , which if you got the pins for connecting the W and hold pins , can allow for upto 4 bit write/ reads - somethin i not seen as example in code

as i have to use a SD and using SDFS3.bas include for it , iwill use some of the same varables so i am not boging down the cpu with more duplicated varables for the buffers ,

see how it goes in the next few days and post the code , cos i really hate doing the wheel if i can avoid ,

Flash chips have advantages in cost/ speed/ size over the EEprom and I2C , even after the need for level converters

one day wish list is that PIC'S have level converters built in on all ports but that a big ask as they dont want to do it it seems

[mackrackit]

Simple answer is to run the PIC at 3.3 volts. In fact, many of the PICs are designed for this voltage. So just make the switch to low power and be done.

[longpole001]

i would have and its only because i have glcd that runs at 5v , as most GLCD do when they are larger that you either run level converters for GLCD interface or you do it for the 3.3v devices , which ever is less , ADC inputs also have to be considered