LTDC not generating clock

[PhilipC]

Hi,

I have a Nucleo-U5A5ZJ-Q board which i replace the mcu with a STM32U5A9ZJT6.

I'm trying to use LTDC to control a 800x480 LCD (WF50FTYAGDNN0#) via RGB888.

Eventually running touchgfx, but I have fallen over at the first hurdle.

I have read many tutorials and forum posts and no one seems to have the same issue as me.

 

I started a blank project and followed this

https://support.touchgfx.com/docs/development/board-bring-up/how-to/03-display-internal

But my display remains a black screen, I then probed PD3 (LTDC_CLK) where I expected the 25Mhz clock signal that was configured, but saw nothing. 

I also tried switching the pins "Max output speed" to Very High as I saw somewhere that this was required.

I then switched PD3 to GPIO_Output and toggled it to make sure connections are correct.

 

Is there something wrong with my clock setup? I tried a test of toggling a pin in the while loop with a 1ms delay and the scope says a full cycle took 4ms instead of the expected 2ms... but then I set the delay to 10ms and eveything is as expected on the scope.

 

Note about the display: it doesn't have Hsync and Vsync lines I assume this means it is permanently in DE mode and I can leave those pins floating from the mcu?

 

Any help would really be appreciated as I have been going at this for a couple of days now.

[PhilipC]

I observed the registers as i stepped through the HAL_LTDC_Init() and none of the LTDC registers are being updated, so LTDC is never setup nor enabled as they aren't being written to... what could cause this?

The init vars do have the cubemx values in them

 

 

[Tesla DeLorean]

Make sure the LTDC clock is explicitly enabled in the RCC

LTDCEN in RCC_APB2ENR

[PhilipC]

Yes, this is set.

 

[PhilipC]

I tried the following and LTDC register will not accept anything.

LTDCRST = 0

LTDCEN = 1

 

 while (1)
 {
 /* USER CODE END WHILE */
	 temp = LTDC->GCR;
	 LTDC->GCR = 1;
 /* USER CODE BEGIN 3 */
 }
 /* USER CODE END 3 */
}

 

 

Could it be something with my clock setup?

 

I added an I2C peripherial and after MX_I2C1_Init() i can see values in the I2C registers, but nothing for LTDC...

 

 

 

[waclawek.jan]

So, which one is it, PLL2 or PLL3?

Read out and check/post relevant RCC registers content.

JW

[PhilipC]

Ah sorry I flipped to PLL3 when experimenting stuff, the code does now also point to PLL3.

Does this look like the PLL3 registers aren't reflecting what the code says?

 

 

 

 

 

void HAL_LTDC_MspInit(LTDC_HandleTypeDef* hltdc)
{
 GPIO_InitTypeDef GPIO_InitStruct = {0};
 RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
 if(hltdc->Instance==LTDC)
 {
 /* USER CODE BEGIN LTDC_MspInit 0 */

 /* USER CODE END LTDC_MspInit 0 */

 /** Initializes the peripherals clock
 */
 PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_LTDC;
 PeriphClkInit.LtdcClockSelection = RCC_LTDCCLKSOURCE_PLL3;
 PeriphClkInit.PLL3.PLL3Source = RCC_PLLSOURCE_HSE;
 PeriphClkInit.PLL3.PLL3M = 1;
 PeriphClkInit.PLL3.PLL3N = 15;
 PeriphClkInit.PLL3.PLL3P = 2;
 PeriphClkInit.PLL3.PLL3Q = 2;
 PeriphClkInit.PLL3.PLL3R = 10;
 PeriphClkInit.PLL3.PLL3RGE = RCC_PLLVCIRANGE_1;
 PeriphClkInit.PLL3.PLL3FRACN = 3072;
 PeriphClkInit.PLL3.PLL3ClockOut = RCC_PLL3_DIVR;
 if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
 {
 Error_Handler();
 }

 /* Peripheral clock enable */
 __HAL_RCC_LTDC_CLK_ENABLE();

 __HAL_RCC_GPIOE_CLK_ENABLE();
 __HAL_RCC_GPIOF_CLK_ENABLE();
 __HAL_RCC_GPIOD_CLK_ENABLE();
 /**LTDC GPIO Configuration
 PE2 ------> LTDC_R0
 PE3 ------> LTDC_R1
 PE4 ------> LTDC_B0
 PE5 ------> LTDC_G0
 PE6 ------> LTDC_G1
 PF13 ------> LTDC_B1
 PE7 ------> LTDC_B6
 PE8 ------> LTDC_B7
 PE9 ------> LTDC_G2
 PE10 ------> LTDC_G3
 PE11 ------> LTDC_G4
 PE12 ------> LTDC_G5
 PE13 ------> LTDC_G6
 PE14 ------> LTDC_G7
 PE15 ------> LTDC_R2
 PD8 ------> LTDC_R3
 PD9 ------> LTDC_R4
 PD10 ------> LTDC_R5
 PD11 ------> LTDC_R6
 PD12 ------> LTDC_R7
 PD14 ------> LTDC_B2
 PD15 ------> LTDC_B3
 PD0 ------> LTDC_B4
 PD1 ------> LTDC_B5
 PD3 ------> LTDC_CLK
 PD6 ------> LTDC_DE
 PE0 ------> LTDC_HSYNC
 PE1 ------> LTDC_VSYNC
 */
 GPIO_InitStruct.Pin = GPIO_PIN_2|GPIO_PIN_3|GPIO_PIN_4|GPIO_PIN_5
 |GPIO_PIN_6|GPIO_PIN_7|GPIO_PIN_8|GPIO_PIN_9
 |GPIO_PIN_10|GPIO_PIN_11|GPIO_PIN_12|GPIO_PIN_13
 |GPIO_PIN_14|GPIO_PIN_15|GPIO_PIN_0|GPIO_PIN_1;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF8_LTDC;
 HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_13;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF8_LTDC;
 HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

 GPIO_InitStruct.Pin = GPIO_PIN_8|GPIO_PIN_9|GPIO_PIN_10|GPIO_PIN_11
 |GPIO_PIN_12|GPIO_PIN_14|GPIO_PIN_15|GPIO_PIN_0
 |GPIO_PIN_1|GPIO_PIN_3|GPIO_PIN_6;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF8_LTDC;
 HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

 /* LTDC interrupt Init */
 HAL_NVIC_SetPriority(LTDC_IRQn, 0, 0);
 HAL_NVIC_EnableIRQ(LTDC_IRQn);
 HAL_NVIC_SetPriority(LTDC_ER_IRQn, 0, 0);
 HAL_NVIC_EnableIRQ(LTDC_ER_IRQn);
 /* USER CODE BEGIN LTDC_MspInit 1 */

 /* USER CODE END LTDC_MspInit 1 */
 }

}

 

 

 

[PhilipC]

I just tried SAI2 peripheral as it is also on APB2, and it can write to its config registers fine.
I can also write to them and read them fine, so something specific to LTDC.
All the documentation I can find just points to LTDCEN being enabled before writing and nothing else, I'm really at a loss here.

SAI2->GCR = 1;

 

[Tesla DeLorean]

@STOne-32 is it possible this could have been fused like the U5A5 with the LTDC disabled? All peripheral registers are presenting as stuck-at-zero

@PhilipC can you provide a clear picture of the top markings of the IC you mounted.

[PhilipC]

So I went to take a photo and couldn't believe my eyes...
I must have got the chips swapped at somepoint after removing the A5.

I have now swapped the A9 on and sure enough getting all the registers and a LTDC_CLK.
Thank you for your input and sorry for the confusion.

The display is now cycling through Black, White, Red, Green, Blue even though I have an empty while(1) but atleast it's a new problem.

I feel like a *** bashing my head against a wall for the past week only to find out I took the A5 off and put it back on... Thank you for you time @Tesla DeLorean 

[STOne-32]

Dear @PhilipC ,

 

Great !  And yes , it happens to all of us :) . 

@Tesla DeLorean  Merci ! 

Ciao,

 

STOne-32