Posted on May 17, 2011 at 12:53Hi, everyone!
I have a program that send a command and receive response via rs-232.
The commands is any length.
And I made a module that receive a command and send response.
I used DMA for it.
My problem is how do I predict command's length in the module?
I configured DMA for the reading as following.
...............................
#define MAX_COMMAND_LEN 400
u8 com_buf[MAX_COMMAND_LEN + 1];
u8 read_end = false;
..................................
void DMA_Channel5_Configuration(void)
{
DMA_InitTypeDef DMA_InitStructure;
/* DMA1 Channel5 (triggered by USART1 Rx event) Config */
DMA_DeInit(DMA1_Channel5);
DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_DR_Base;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)com_buf;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = MAX_COMMAND_LEN; DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel5, &DMA_InitStructure);
}
void DMA1_Channel5_IRQHandler(void)
{
u16 w_nCmdCode;
if(DMA_GetITStatus(DMA1_IT_TC5) == SET){
read_end = TRUE;
}
}
.......................................
void main()
{
..........
while(read_end == TRUE){
Process();
SendResponse();
read_end == FALSE;
}
..........
}
Now I could not predict the command's length,therefore wrote as DMA_InitStructure.DMA_BufferSize = MAX_COMMAND_LEN;
And the length of command which the program send must be equal to MAX_COMMAND_LEN. So I added dummy bytes(400-16 = 384 bytes) to end of 16byte command .
This works OK, but it is very non-efficient and slow when baudrate is low.
Please help.
Regards.
[ This message was edited by: jki79ros81 on 21-11-2008 09:16 ]
