How to get a TouchGFX demo working in DSI Video Mode

[OLync.1]

I want to verify that the STM32L4R9 discovery kit can work in DSI video mode so that I can port the application to use a display driver that does not have a graphics buffer. I started with the TouchGFXWatch example and have that working. I then used TouchGFX Generator to change the Display Interface to Parallel RCB (LTDC) (per advice from the forum). This resulted in the initial display but no update. I then changed DSIHost to Video Mode which resulted in stripy noise being displayed. I believe I am using the latest versions of all the tools: TouchGFX 4.19, CubeMX 6.5.0, STM32CubeIDE 1.8.0.

My forum reading suggests that this is hard, but possible. Can anyone enlighten me on what I need to modify under the hood to get this to work?

[OLync.1]

Things have substantially improved - I found settings from a HAL file for the board and the display is almost there. FMC settings:

 hsram1.Init.NSBank = FMC_NORSRAM_BANK1;
 hsram1.Init.DataAddressMux = FMC_DATA_ADDRESS_MUX_DISABLE;
 hsram1.Init.MemoryType = FMC_MEMORY_TYPE_PSRAM;
 hsram1.Init.MemoryDataWidth = FMC_NORSRAM_MEM_BUS_WIDTH_16;
 hsram1.Init.BurstAccessMode = FMC_BURST_ACCESS_MODE_DISABLE;
 hsram1.Init.WaitSignalPolarity = FMC_WAIT_SIGNAL_POLARITY_HIGH;
 hsram1.Init.WaitSignalActive = FMC_WAIT_TIMING_BEFORE_WS;
 hsram1.Init.WriteOperation = FMC_WRITE_OPERATION_ENABLE;
 hsram1.Init.WaitSignal = FMC_WAIT_SIGNAL_DISABLE;
 hsram1.Init.ExtendedMode = FMC_EXTENDED_MODE_DISABLE;
 hsram1.Init.AsynchronousWait = FMC_ASYNCHRONOUS_WAIT_DISABLE;
 hsram1.Init.WriteBurst = FMC_WRITE_BURST_DISABLE;
 hsram1.Init.ContinuousClock = FMC_CONTINUOUS_CLOCK_SYNC_ASYNC;
 hsram1.Init.WriteFifo = FMC_WRITE_FIFO_DISABLE;
 hsram1.Init.NBLSetupTime = 0;
 hsram1.Init.PageSize = FMC_PAGE_SIZE_NONE;

Timings:

 Timing.AddressSetupTime = 1;
 Timing.AddressHoldTime = 0;
 Timing.DataSetupTime = 5;
 Timing.BusTurnAroundDuration = 1;
 Timing.CLKDivision = 2;
 Timing.DataLatency = 2;
 Timing.AccessMode = FMC_ACCESS_MODE_A;

But I don't think they match the device timings (attached). I've experimented with many values and what I have is close to working but not quite there. Can anyone with a better understanding of PSRAM timings advise?

[RetroInTheShade]

Hi Olync,

I'm not an expert on PSRAM but digging around, there does look to be an example FMC project for your disco on the ST repository.

The example uses the following timing:

 SRAM_Timing.AddressSetupTime = 5;
 SRAM_Timing.AddressHoldTime = 1; /* Min value, Don't care on SRAM Access mode A */
 SRAM_Timing.DataSetupTime = 3;
 SRAM_Timing.BusTurnAroundDuration = 1; 
 SRAM_Timing.CLKDivision = 2; /* Min value, Don't care on SRAM Access mode A */
 SRAM_Timing.DataLatency = 2; /* Min value, Don't care on SRAM Access mode A */

The clock is the example is configured at 80MHz or (12.5ns period) so these settings seem reasonable compared to datasheet specifications.

Cheers.

[OLync.1]

Thanks all for your help, I finally got it working with double buffering in PSRAM. The last hurdle was annoying full screen glitches periodically. I tracked it down to this framework-generated code:

void TouchGFXHAL::setTFTFrameBuffer(uint16_t* adr)
{
 if (doubleBufferingEnabled)
 {
 HAL_DSI_Stop(&hdsi);
 
 currFbBase = adr;
 
 /* Update LTDC layers base address */
 if (HAL_LTDC_SetAddress(&hltdc, (uint32_t)currFbBase, 0) != HAL_OK)
 {
 while (1);
 }
 __HAL_LTDC_LAYER_ENABLE(&hltdc, 0);
 __HAL_LTDC_RELOAD_IMMEDIATE_CONFIG(&hltdc);
 
 HAL_DSI_Start(&hdsi);
 }
}

I commented out the HAL_DSI_Stop and HAL_DSI_Start - hey presto, no flicker! Not sure how legit it is but it's working!