From f840b0925a76cb1efd7001befa5484da6eaa0cce Mon Sep 17 00:00:00 2001
From: Bart Van Der Meerssche <bart.vandermeerssche@flukso.net>
Date: Mon, 16 Nov 2009 00:56:00 +0000
Subject: [PATCH] uc: implement 16x16 -> 32 unsigned MAC macro

---
 uc/main.c |  7 +++++--
 uc/main.h | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/uc/main.c b/uc/main.c
index 6fa1ac9..c03ec45 100644
--- a/uc/main.c
+++ b/uc/main.c
@@ -1,5 +1,5 @@
 //
-// main.1mhz.c : AVR uC code for flukso sensor board
+// main.c : AVR uC code for flukso sensor board
 // Copyright (c) 2008-2009 jokamajo.org
 //
 // This program is free software; you can redistribute it and/or
@@ -70,7 +70,8 @@ ISR(PCINT2_vect) {
 ISR(TIMER2_OVF_vect) {
   // read ADC result
   // add to nano(Wh) counter
-  aux[0].nano += (uint32_t)METERCONST * ADC;
+  MacU16X16to32(aux[0].nano, METERCONST, ADC);
+
   if (aux[0].nano > 1000000000) {
      measurements[0].value++;
      aux[0].pulse = true;
@@ -269,6 +270,8 @@ int main(void)
   for (i=0; i<4; i++) _delay_ms(5000);
 
   serialFlush();
+  printString("\n");
+
   WDT_on();
 
   for (;;) loop();
diff --git a/uc/main.h b/uc/main.h
index 06b6858..6287167 100644
--- a/uc/main.h
+++ b/uc/main.h
@@ -1,5 +1,5 @@
 //
-// main.1mhz.h : AVR uC header file for flukso sensor board
+// main.h : AVR uC header file for flukso sensor board
 // Copyright (c) 2008-2009 jokamajo.org
 //
 // This program is free software; you can redistribute it and/or
@@ -49,6 +49,37 @@
 #define END1 0xdddddddd
 #define END0 0xcccccccc
 
+
+// This macro performs a 16x16 -> 32 unsigned MAC in 37 cycles with operands and results in memory
+// based on http://www2.ife.ee.ethz.ch/~roggend/publications/wear/DSPMic_v1.1.pdf par 3.4 and table 31.
+#define MacU16X16to32(uint_32Acc, uint_16In1, uint_16In2) \
+asm volatile ( \
+  "clr r2 \n\t" \
+  "mul %B2, %B1 \n\t" \
+  "movw r4, r0 \n\t" \
+  "mul %A2, %A1 \n\t" \
+  "add %A0, r0 \n\t" \
+  "adc %B0, r1 \n\t" \
+  "adc %C0, r4 \n\t" \
+  "adc %D0, r5 \n\t" \
+  "mul %B2, %A1 \n\t" \
+  "add %B0, r0 \n\t" \
+  "adc %C0, r1 \n\t" \
+  "adc %D0, r2 \n\t" \
+  "mul %A2, %B1 \n\t" \
+  "add %B0, r0 \n\t" \
+  "adc %C0, r1 \n\t" \
+  "adc %D0, r2 \n\t" \
+  "clr r1 \n\t" \
+  : \
+  "+r" (uint_32Acc) \
+  : \
+  "a" (uint_16In1), \
+  "a" (uint_16In2) \
+  : \
+  "r2", "r4", "r5" \
+)
+
 // datastructures
 struct state {
   boolean pulse;