I have just been thinking if there is any way to use 2 flash chips one with the stock firmware and one with openwrt on and a switch to select between them. Is it just as simple as isolating the power to each chip ?

Thanks Nikki x

Yes you can just switch the chip select lines (pin 1 on an 8 pin SPI flash).  The other 7 pins are connected in parallel.  You need pull-up resistors so that the chip that is switched off stays unselected.

I have done this to install larger chips.  Solder a new chip on top of the old one, except pin 1. Use serial console on the bootloader to copy the bootloader into the blank new chip. Then I removed the switching arrangement and permanently wired the new chip to select, and CS of the old chip to 3.3 volts.   The wires can be moved use the old chip as a backup if needed.

(Last edited by mk24 on 13 May 2017, 17:13)

Thank you. I have just found this circuit diagram are the diodes needed ?

blog.jacksoftlabs.com/images/vaiogeddon/dualbiosdiagram.png

sorry the forum will not allow me to attach a image

Thanks Nikki x

That picture is a very strange way to do it.

What I did was connect the board CS to the arm of the switch.  Each chip connects to one end of the switch and also has a resistor to +3.3 volts.  So the chip that is switched on has a direct drive of CS from the board, while the one that is switched off has its CS pin pulled up to 3.3 volts by its resistor.  The board is also driving the resistor of the active chip, but that is not going to affect it.

(Last edited by mk24 on 13 May 2017, 20:21)

thank you I will give it a try. hopefully I wont blow anything up :-p

nikki x

Please give us the diagram for 2 flash.