Dumping SPI RAM frame buffer to SPI LCD directly

[Koen]

Hello,

       is it somewhat possible to transfer directly from a SPI RAM chip to a SPI LCD ?

       The microcontroller would set up both for it but then the SPI RAM would transfer the pixels to the LCD directly without involving the microcontroller ?

       I feel like I've seen something similar for SDRAM and parallel LCD interface.

Thank you !
Koen

[jhpadjustable]

TFT LCDs generally accept raw raster data and sync pulses and shift it directly into the LCD matrix, and do not have their own command processors on board. SPI LCDs have a somewhat intelligent controller which has its own integrated frame buffer RAM and command processor, which only gets in the way of such a scheme. Yes, you could, but it would be redundant and pointless. The only adjacent worthwhile application that comes to mind would be for a very limited MCU (PIC16-class) to send fixed images and supporting commands from an external serial flash to a disproportionately large SPI LCD.

[SiliconWizard]

Given that both devices have a slave SPI interface, you can't. (At least I've never run into any SPI RAM or SPI LCD that could act as a master.)

The usual way would be to set up DMA transfers within your MCU, which would take almost no CPU time (apart from starting the transfers, a couple of cycles if done right). If it doesn't support DMA, you're out of luck. Of course you could always add some kind  of small FPGA/CPLD in between to take care of the transfers, but I guess that would be way beyond what you intended to do.

[Gribo]

You can try and hack it and connect them in daisy chain, MCU data out to DRAM data in, DRAM data out to LCD, with CS lines to allow configuration of LCD. Good luck.