From f683cff9e20b709bbf5508a81b84f65f27191dbf Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Sun, 13 Jan 2013 19:26:33 +1100
Subject: [PATCH] DataFlash: speed up SPI transfers in DataFlash_APM1

---
 libraries/DataFlash/DataFlash_APM1.cpp | 78 +++++++++++---------------
 1 file changed, 32 insertions(+), 46 deletions(-)

diff --git a/libraries/DataFlash/DataFlash_APM1.cpp b/libraries/DataFlash/DataFlash_APM1.cpp
index 21a423b7ef..96503998a3 100644
--- a/libraries/DataFlash/DataFlash_APM1.cpp
+++ b/libraries/DataFlash/DataFlash_APM1.cpp
@@ -187,19 +187,17 @@ void DataFlash_APM1::PageToBuffer(uint8_t BufferNum, uint16_t PageAdr)
     // activate dataflash command decoder
     _spi->cs_assert();
 
-    if (BufferNum==0)
-        _spi->transfer(DF_TRANSFER_PAGE_TO_BUFFER_1);
-    else
-        _spi->transfer(DF_TRANSFER_PAGE_TO_BUFFER_2);
-
+    uint8_t cmd[4];
+    cmd[0] = BufferNum?DF_TRANSFER_PAGE_TO_BUFFER_2:DF_TRANSFER_PAGE_TO_BUFFER_1;
     if(df_PageSize==512) {
-        _spi->transfer((uint8_t)(PageAdr >> 7));
-        _spi->transfer((uint8_t)(PageAdr << 1));
+        cmd[1] = (uint8_t)(PageAdr >> 7);
+        cmd[2] = (uint8_t)(PageAdr << 1);
     }else{
-        _spi->transfer((uint8_t)(PageAdr >> 6));
-        _spi->transfer((uint8_t)(PageAdr << 2));
+        cmd[1] = (uint8_t)(PageAdr >> 6);
+        cmd[2] = (uint8_t)(PageAdr << 2);
     }
-    _spi->transfer(0x00); // don´t care bytes
+    cmd[3] = 0;
+    _spi->transfer(cmd, sizeof(cmd));
 
     //initiate the transfer
     _spi->cs_release();
@@ -216,19 +214,17 @@ void DataFlash_APM1::BufferToPage (uint8_t BufferNum, uint16_t PageAdr, uint8_t
     // activate dataflash command decoder
     _spi->cs_assert();
 
-    if (BufferNum==0)
-        _spi->transfer(DF_BUFFER_1_TO_PAGE_WITH_ERASE);
-    else
-        _spi->transfer(DF_BUFFER_2_TO_PAGE_WITH_ERASE);
-
+    uint8_t cmd[4];
+    cmd[0] = BufferNum?DF_BUFFER_2_TO_PAGE_WITH_ERASE:DF_BUFFER_1_TO_PAGE_WITH_ERASE;
     if(df_PageSize==512) {
-        _spi->transfer((uint8_t)(PageAdr >> 7));
-        _spi->transfer((uint8_t)(PageAdr << 1));
+        cmd[1] = (uint8_t)(PageAdr >> 7);
+        cmd[2] = (uint8_t)(PageAdr << 1);
     }else{
-        _spi->transfer((uint8_t)(PageAdr >> 6));
-        _spi->transfer((uint8_t)(PageAdr << 2));
+        cmd[1] = (uint8_t)(PageAdr >> 6);
+        cmd[2] = (uint8_t)(PageAdr << 2);
     }
-    _spi->transfer(0x00); // don´t care bytes
+    cmd[3] = 0;
+    _spi->transfer(cmd, sizeof(cmd));
 
     //initiate the transfer
     _spi->cs_release();
@@ -250,28 +246,20 @@ void DataFlash_APM1::BlockWrite (uint8_t BufferNum, uint16_t IntPageAdr,
     // activate dataflash command decoder
     _spi->cs_assert();
 
-    if (BufferNum==0)
-        _spi->transfer(DF_BUFFER_1_WRITE);
-    else
-        _spi->transfer(DF_BUFFER_2_WRITE);
-
-    _spi->transfer(0x00);									// don't care
-    _spi->transfer((uint8_t)(IntPageAdr>>8));       // upper part of internal buffer address
-    _spi->transfer((uint8_t)(IntPageAdr));          // lower part of internal buffer address
-
-    const uint8_t *pData;
+    uint8_t cmd[4];
+    cmd[0] = BufferNum?DF_BUFFER_2_WRITE:DF_BUFFER_1_WRITE;
+    cmd[1] = 0;
+    cmd[2] = (uint8_t)(IntPageAdr>>8);
+    cmd[3] = (uint8_t)(IntPageAdr);
+    _spi->transfer(cmd, sizeof(cmd));
 
     // transfer header, if any
-    pData = (const uint8_t *)pHeader;
-    while (hdr_size--) {
-        _spi->transfer(*pData++);
+    if (hdr_size != 0) {
+        _spi->transfer((const uint8_t *)pHeader, hdr_size);
     }
 
     // transfer data
-    pData = (const uint8_t *)pBuffer;
-    while (size--) {
-        _spi->transfer(*pData++);
-    }
+    _spi->transfer((const uint8_t *)pBuffer, size);
 
     // release SPI bus for use by other sensors
     _spi->cs_release();
@@ -286,15 +274,13 @@ bool DataFlash_APM1::BlockRead(uint8_t BufferNum, uint16_t IntPageAdr, void *pBu
     // activate dataflash command decoder
     _spi->cs_assert();
 
-    if (BufferNum==0)
-        _spi->transfer(DF_BUFFER_1_READ);
-    else
-        _spi->transfer(DF_BUFFER_2_READ);
-
-    _spi->transfer(0x00);
-    _spi->transfer((uint8_t)(IntPageAdr>>8)); 		// upper part of internal buffer address
-    _spi->transfer((uint8_t)(IntPageAdr));   		// lower part of internal buffer address
-    _spi->transfer(0x00);                          		// don't cares
+    uint8_t cmd[5];
+    cmd[0] = BufferNum?DF_BUFFER_2_READ:DF_BUFFER_1_READ;
+    cmd[1] = 0;
+    cmd[2] = (uint8_t)(IntPageAdr>>8);
+    cmd[3] = (uint8_t)(IntPageAdr);
+    cmd[4] = 0;
+    _spi->transfer(cmd, sizeof(cmd));
 
     uint8_t *pData = (uint8_t *)pBuffer;
     while (size--) {