Posted on May 28, 2017 at 20:40
Hi!
I`m trying to send data from memory to SPI using DMA for LCD TFT purposes. To speed up the drawing I would like to send the same half-word x times (fill the rectange with the same color for example). At this point I`m able to send correcty the data to defined SPI port from particular memory adress (without memory incrase since I would like to send the same data over and over again) . The issue is that the DMA command only allows me to send 8bit data and I need to use 16 bits (half-word).
The question - is there any possibility to send half-word (without memory increase by DMA) to SPI (instead of 8bits only)?
LCD_WriteReg(0x0020, 0 );//set x coordinate do TFT
LCD_WriteReg(0x0021, 0 );//set z coordinate do TFT
SendIndex(0x0022);//send data
SendDataStart(); color=color+1250;uint16_t i;
for (i=0;i<30;i++){ HAL_SPI_Transmit_DMA(&hspi1, (uint8_t*)&color, 1024*5); //<===== Eight bits only, I need 16 bits while(HAL_SPI_GetState(&hspi1) != HAL_SPI_STATE_READY);}SendDataEnd();
best regards
Rafal
#stm32f103c8cb-hal-library-with-spi-over-dma
Posted on May 30, 2017 at 22:53
ChrisH,
Thank You so much for sugesstion, that would work if I would not need to send 24 bits as general commands. I`m communicating with LCD thru R61505W TFT contoller. that kind communication requires in general command of 24 bits as below:
so if I change the 8 bits to 16 bits that makes instead of sending 3 bytes (- refering to above picture ) two halfwords (which does not corespond to above diagram)
byte1 (Device ID code+RS+RW)
byte2 (MSB 8 bits)
byte3 (LSB 8 bits)
total 24 bits as required above
If I switch to 16 bits I would have to send
halfword1 (16 bits)
halfword2 (16 bits)
(32 bits in total -does not match 24 bits)
so in general as example instead of sending command as example
0x70 (device ID Code+RS+RW 8 bits)
0x34 (MSB 8 bits)
0x65 (LSB 8 bits)
after switching to 16 bits I woud have to send command as
0x0070
(device ID Code+RS+RW BUT THAT WOULD BE 16 bits -wrong)
0x3465 (MSB+LSB 16 bits)
and that would not match the timming graph above.
So, maybe I would have to stick with 8 bits and at some point will have to switch to 16 bits where in need to transfer thru DMA?
How can I switch from 8 to 16bits in runtime?
I hope I dont have to reconfigure thru ''Init'' statement as below? Is there any other way?
hspi1.Instance = SPI1;
hspi1.Init.Mode = SPI_MODE_MASTER; hspi1.Init.Direction = SPI_DIRECTION_2LINES; hspi1.Init.DataSize = SPI_DATASIZE_16BIT; hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH; hspi1.Init.CLKPhase = SPI_PHASE_2EDGE; hspi1.Init.NSS = SPI_NSS_SOFT; hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_2; hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB; hspi1.Init.TIMode = SPI_TIMODE_DISABLE; hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE; hspi1.Init.CRCPolynomial = 10; if (HAL_SPI_Init(&hspi1) != HAL_OK) { Error_Handler(); }best regards
Rafal
