MMAP an external SPI device on the T4.0

[Jean-Marc]

I am currently experimenting with PSRAM on the Teensy 4.0.

I finally got an IPS6404 (8MB RAM) working on the SPI2 bus of the Teensy4.0.
Speed can still be improved but I am not using DMA transfer nor QUAD SPI yet.
Anyhow...

This kind of device is only useful for me if I can MMAP the device to a part of the memory map. I currently have a read() and a write() function that handle the paging/caching into real memory but I would like to be able to use pointers to that memory that I can use from C directly without having to call my read/write function.

Is there an example on how to do this.
Is there a memory space that can be used to address 8MB?

[macrosii]

Sorry, cant help with the question, but would like to try out the PSRAM chips. Did you get them from Electrodragon ? if so were there package ok for MSL3 ? I am in the uk and imagine they will take some time to arrive. Also would you mind share the code you have so far ?

Thanks and Regards

[Jean-Marc]

I bought them at Electrodragon.
https://www.electrodragon.com/produc...s6404-iot-ram/
The SMD package 3.3v version.
I am from Belgium. It took 2-3 weeks.
I ordered 8 and I got something like twice as much.
I started to use it for my emulator project (https://github.com/Jean-MarcHarvengt/MCUME) but I cannot make it work as fast as it should. I made a driver that can cache few pages. It runs roughly half what it should on the T4
I am not using Quad SPI yet.
I will publish the 1st emulator using it with pictures later this W-E.

[macrosii]

Many thanks for the info. Just wondering did you have any trouble with Moisture Sensitivity Level ? Did you have to bake them or just careful hand soldering ?

Great work by the way on your emulators!

[Jean-Marc]

I am not an expert of SMD soldering but I managed to solder it without any problem. I use flux. It helps a lot for me as I don't have specific equipment for SMD. No issue with MSL also.

The PC engine emulator has been added by the way.
See code and video at https://github.com/Jean-MarcHarvengt/MCUME