#include "LPC17xx.h"
#include "base/ssp_prv.h"

Include dependency graph for ssp1.h:

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Functions
unsigned	ssp1_dma_transfer_block (unsigned char *pBuffer, uint32_t num_bytes, char is_write_op)

Function Documentation

unsigned ssp1_dma_transfer_block	(	unsigned char *	pBuffer,
		uint32_t	num_bytes,
		char	is_write_op
	)

Transfers data over SPI (SSP#1)

Parameters

pBuffer	The read or write buffer
num_bytes	The length of the transfer in bytes
is_write_op	Non-zero for Write-operation, zero for read operation

Note

If is_write_op is true:

SPI data is sent from pBuffer
SPI data is copied from SSP DR to dummy buffer and discarded If is_write_op is false (read operation) :
SPI data is copied from SSP DR to pBuffer
0xFF is sent out for each byte transfered

Returns: 0 upon success, or non-zero upon failure.

TO DO : Optimize SSP1 DMA

Try setting source and destination burst size to 4
Try setting 16-bit SPI, and source and destination width to 1 WORD

LPC_SSP1->CR0 : B3:B0. 0b0111 = 8-bit and 0b1111 = 16-bit LPC_SSP1->CR0 |= (1<<3); // 16-bit LPC_SSP1->CR0 &= ~(1<<3); // 8-bit

Bits of DMACCControl: Transfer size: B11:B0 Source Burst Size: B14:B12 - 0:1, 1:4, 2:8, 3:16 bytes Dest. Burst Size: B17:B15 - 0:1, 1:4, 2:8, 3:16 bytes Source Width: B20:B18 - 0:Byte, 1:Word, 2:DWORD Dest. Width: B23:B21 - 0:Byte, 1:Word, 2:DWORD Source increment: B26 Destination increment: B27 Terminal count interrupt enable: B31

Bits of DMACCConfig: Enable: B0 Source Peripheral: B5:B1 (ignored if source is memory) Dest. Peripheral: B10:B6 (ignored if dest. is memory) Transfer type: B13:B11 - See below Interrupt Error Mask: B14 Terminal Count Interrupt : B15

Bits for transfer type: 000 - Memory to Memory 001 - Memory to Peripheral 010 - Peripheral to Memory 011 - Source peripheral to destination peripheral

Clear existing terminal count and error interrupts otherwise DMA will not start.

From SPI to buffer: For write operation :

Receive data into dummy buffer
Don't increment destination For read operation:
Read data into pBuffer
Increment destination

From buffer to SPI : For write operation :

Source data is pBuffer
Increment source data For read operation:
Source data is buffer with 0xFF
Don't increment source data

Channel must be fully configured and then enabled separately. Setting DMACR's Rx/Tx bits should trigger the DMA

Functions

Function Documentation