Hi!

I have Riverdy's EVE4 IPS 10.1" LCD TFT (type RVT101HVBNWC00-B), which is run by BT817Q.

I noticed that my application can not take full advantage of DL memory in BT817Q.

To further investigate the problem I wrote simple test program:

   printf("\r\n ------------------------------------------------ \r\n");
uint32_t c = 1091;
//uint32_t c = 2038;


Gpu_Copro_SendCmd(phost, CMD_COLDSTART);
Gpu_Copro_SendCmd(phost, CMD_DLSTART);
Gpu_Copro_SendCmd(phost, CLEAR_COLOR_RGB(0, 0, 0));
Gpu_Copro_SendCmd(phost, CLEAR(1, 1, 1));

for(uint32_t i = 0; i < c; i++)
{
Gpu_Copro_SendCmd(phost, NOP());
//Gpu_Copro_SendCmd(phost, TAG(1));
}

Gpu_Copro_SendCmd(phost, COLOR_RGB(255, 0, 0));
Gpu_Copro_SendCmd(phost, VERTEX_FORMAT(3));
Gpu_Copro_SendCmd(phost, BEGIN(LINE_STRIP));
Gpu_Copro_SendCmd(phost, LINE_WIDTH(5 * 16));
Gpu_Copro_SendCmd(phost, VERTEX2F(10 * 8, 10 * 8));
Gpu_Copro_SendCmd(phost, VERTEX2F(500 * 8, 500 * 8));
Gpu_Copro_SendCmd(phost, END());

Gpu_Copro_SendCmd(phost, DISPLAY());
Gpu_Copro_SendCmd(phost, CMD_SWAP);

uint32_t reg_REG_CMD_DL = Gpu_Hal_Rd32 (phost, REG_CMD_DL);

printf("reg_REG_CMD_DL = %d        c = %d \r\n", reg_REG_CMD_DL, c);

If I run this program I can go with variable “c”, which is filling up DL memory with dummy NOP command up to value 1091. If “c” becomes 1092, red line on screen starts having artifacts.

Printf command for last stable c = 1091 returns:

reg_REG_CMD_DL = 4404        c = 1091

So here we have magical upper limit of DL’s memory at 4404 bytes. 

This is strange because DL's size should be 8191, according to manual.

Further tinkering revealed that if I fill DL’s memory with another dummy command like TAG(1) behaviour changes.

For instance if I remove lines of code (comment them):

uint32_t c = 1091;
…and
Gpu_Copro_SendCmd(phost, NOP());

…and uncomment lines:
//uint32_t c = 2038;
…and
//Gpu_Copro_SendCmd(phost, TAG(1));

…my test application behaves as expected. I can go with variable “c” up to 2038.

In this case printf returns:

reg_REG_CMD_DL = 8191        c = 2038

…for last stable “c”. For c = 2039 and above, screen turns black, i.e. DL’s memory overflows.

Can somebody explain this?

I my actual application I am not filling DL’s memory with dummy code like in above example, instead I am filling it up with graphics primitives (lines, dots, circles etc), however when DL’s fullness reaches 4404, display starts displaying gibberish.