STM32L4R9ZI-Eval External SRAM shortage for 800x480 TFT LCD Frame Buffer.

[Ashvin Ramani]

We have the STM32L4R-Eval kit revision 01 as well as revision 02

We want to use STM32L4R9AI in our prototype, which was used in the above Eval.

The difference between these two versions looks like in revision01 U5 SRAM is populated but not working correctly; in revision02 it wasn't populated. Please Confirm.

We want to use STM32L4R9AI in our prototype, which was used in the above Eval and our prototype is not ready yet, So, we want to start our development using eval-kit and our product requires 800x480 resolution TFT LCD on RGB interface.

This is the list of challenges we are facing as per below:

1) As per our display resolution required frame buffer size for double buffering is around 2MB that can not be fit into internal RAM(640KB). So want to use external SRAM.

Now, we have two options:

2) Option1: Use external SRAM connected to OCTO SPI2 SRAM(U5 IC) but it was not originally populated because of some limitations as per its datasheet.

-> Is this limitation specific to the Eval kit only or same can be applicable to MCU as well which we want to use in our prototype?

->Is this limitation related to part IS66WVH8M8BLL-100BLI, because we are planning to use the same in our prototype?

3) Option2: Use external SRAM FMC interface but as per datasheet can not be used with RGB interface.

-> Please suggest any workaround.

4) Can we use an external OCTO SPI1 flash to store the frame buffer for TFT LCD or it should only use to store UI bitmap, image, and UI contains?

5) @ST Kindly suggest a possible solution to start our UI development with Eval-kit, We are planning to use TouchGFX for UI creation but looks like we don't have any external memory to store the LCD frame buffer.

6)Is this MCU series fine to go with 800x480 resolution LCD or are you suggesting any other one?

[Tesla DeLorean]

Probably why it ships with smaller resolution screens?

​

Bigger screens, get a part supporting external SDRAM, and QSPI/OSPI NOR Flash, plenty of capable H7 parts

[Ashvin Ramani]

@Community member​ , Originally shipped 480x272 resolution with Eval board but our product demands 800x480 resolution TFT LCD, where looks like need to use external RAM.

Please go through my post and try to answer each point. Thanks

[Tesla DeLorean]

I chose option 3 as your proposed options are unworkable, and you seem inflexible.

​

Y​ou'll either need to develop using the smaller screen, use a single memory buffer, or screen side buffer.

​

B​andwidth constrained device get to be increasingly less viable as resolution expands as a function of area.

​

Suggest you sell boards you have, and buy closer proxies which have the external memory you ​need and the screen resolution you demand.

[Ashvin Ramani]

@Community member​ , Thanks for your suggestion, but changing MCU Part in the actual prototype bring lots of rework in design, still my questions under option1, point4/5 are unanswered. I am looking for an inline answer from @ST. Thanks

[Ashvin Ramani]

@ST, Can you please look here as it was quite important!

[Ashvin Ramani]

@ST, May I have any update on this?

[FBL]

Hello @Ashvin Ramani​ ,

"The difference between these two versions looks like in revision01 U5 SRAM is populated but not working correctly; in revision02 it wasn't populated. Please Confirm."

> These are the main changes between the two versions

L3 changed into MURATA BNX002-11

T2, T3, T4, T5, T6, T7, T8 changed into NXP PMN30XP

U11 changed into MACRONIX MT28EW128ABA1LPC-0SIT

U30, U31 changed into STMICROELECTRONICS IMP34DT05TR

U5 ISSI IS66WVH8M8BLL-100BLI changed into "Not fitted"

Regarding LCD-TFT display controller, I think following application note AN4861 may be helpful.

[Tesla DeLorean]

I think that's a MICRON part, not MACRONIX, for the Parallel NOR Flash

https://www.digikey.com/en/products/detail/micron-technology-inc/MT28EW128ABA1LPC-0SIT-TR/6595521

Background images could likely be pulled from that.

For the OCTOSPI NOR Flash (U6)

MACRONIX: MX25LM51245GXDI00 (FITTED ?)

MICRON: MT35XL512ABA1G12-0SIT 

[FBL]

Indeed MT35XL512ABA1G12-0SIT is MICRON, but both reference parts are supported.

For U6, only resistors R202 R212, also TP4 VPP (measurement point) are not fitted,

which means chip select C2 for example is no longer activated by hardware but by OCTOSPI_NCS.

Please find more details in the schematic MB1313-L4R9I-B02.

[FBL]

A section to describe all versions and differences between products will be added when updating UM2448.

Internal ticket number: 134337 (This is an internal tracking number and is not accessible or usable by customers).

[Ashvin Ramani]

@F.Belaid​ , Thank you for your answer.

But my question is still open, can you please answer it point by point from the original post starting 1) to 6)?

Thanks in advance!