From 0bda21a3fc5a73f13df4d63d4f8622706dcec813 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Mon, 28 Oct 2013 18:20:20 +1100
Subject: [PATCH] HAL_AVR: changed to 16 byte bulk transfer on SPI0

---
 libraries/AP_HAL_AVR/SPIDevice_SPI0.cpp | 13 +++++++------
 libraries/AP_HAL_AVR/SPIDevices.h       |  2 +-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/libraries/AP_HAL_AVR/SPIDevice_SPI0.cpp b/libraries/AP_HAL_AVR/SPIDevice_SPI0.cpp
index 853c1b024d..e52b95421c 100644
--- a/libraries/AP_HAL_AVR/SPIDevice_SPI0.cpp
+++ b/libraries/AP_HAL_AVR/SPIDevice_SPI0.cpp
@@ -76,7 +76,7 @@ uint8_t AVRSPI0DeviceDriver::_transfer(uint8_t data)
    a specialised transfer function for the MPU6k. This saves 2 usec
    per byte
  */
-void AVRSPI0DeviceDriver::_transfer15(const uint8_t *tx, uint8_t *rx) 
+void AVRSPI0DeviceDriver::_transfer16(const uint8_t *tx, uint8_t *rx) 
 {
     spi0_transferflag = true;
 #define TRANSFER1(i) do { SPDR = tx[i];  while(!(SPSR & _BV(SPIF))); rx[i] = SPDR; } while(0)
@@ -95,6 +95,7 @@ void AVRSPI0DeviceDriver::_transfer15(const uint8_t *tx, uint8_t *rx)
     TRANSFER1(12);
     TRANSFER1(13);
     TRANSFER1(14);
+    TRANSFER1(15);
     spi0_transferflag = false;
 }
 
@@ -112,11 +113,11 @@ void AVRSPI0DeviceDriver::transaction(const uint8_t *tx, uint8_t *rx,
             _transfer(tx[i]);
         }
     } else {
-        while (len >= 15) {
-            _transfer15(tx, rx);
-            tx += 15;
-            rx += 15;
-            len -= 15;
+        while (len >= 16) {
+            _transfer16(tx, rx);
+            tx += 16;
+            rx += 16;
+            len -= 16;
         }
         for (uint16_t i = 0; i < len; i++) {
             rx[i] = _transfer(tx[i]);
diff --git a/libraries/AP_HAL_AVR/SPIDevices.h b/libraries/AP_HAL_AVR/SPIDevices.h
index 7eb1ed6e5f..021fd645ce 100644
--- a/libraries/AP_HAL_AVR/SPIDevices.h
+++ b/libraries/AP_HAL_AVR/SPIDevices.h
@@ -36,7 +36,7 @@ private:
     void _cs_release();
     uint8_t _transfer(uint8_t data);
     // used for MPU6k
-    void _transfer15(const uint8_t *tx, uint8_t *rx);
+    void _transfer16(const uint8_t *tx, uint8_t *rx);
 
     static AP_HAL_AVR::AVRSemaphore _semaphore;