From 0ce3be2f3431e9652d7831650c7f916e3d8afe2e Mon Sep 17 00:00:00 2001
From: Philippe Teuwen <phil@teuwen.org>
Date: Wed, 10 Jun 2020 00:06:18 +0200
Subject: [PATCH] Reintroduce AvgAdv, avoid *64 as it could easily overflow

This reverts partly commit 9189dc85635af754556b2803033574d425b67146.
---
 armsrc/appmain.c  | 21 ++++++++++++---------
 armsrc/appmain.h  |  1 +
 armsrc/thinfilm.c |  4 ++--
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index 9e51d0f76..c5cdc5dc7 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -137,11 +137,14 @@ static uint16_t ReadAdc(int ch) {
 }
 
 // was static - merlok
+uint16_t AvgAdc(int ch) {
+    return SumAdc(ch, 32) >> 5;
+}
+
 uint16_t SumAdc(int ch, int NbSamples) {
     uint16_t a = 0;
     for (uint8_t i = 0; i < NbSamples; i++)
         a += ReadAdc(ch);
-
     return (a + (NbSamples >> 1) - 1);
 }
 
@@ -225,9 +228,9 @@ static void MeasureAntennaTuning(void) {
 static uint16_t MeasureAntennaTuningHfData(void) {
 
 #if defined RDV4
-    return (MAX_ADC_HF_VOLTAGE_RDV40 * SumAdc(ADC_CHAN_HF_RDV40, 64)) >> 16;
+    return (MAX_ADC_HF_VOLTAGE_RDV40 * SumAdc(ADC_CHAN_HF_RDV40, 32)) >> 15;
 #else
-    return (MAX_ADC_HF_VOLTAGE * SumAdc(ADC_CHAN_HF, 64)) >> 16;
+    return (MAX_ADC_HF_VOLTAGE * SumAdc(ADC_CHAN_HF, 32)) >> 15;
 #endif
 
 }
@@ -540,7 +543,7 @@ void ListenReaderField(uint8_t limit) {
     LEDsoff();
 
     if (limit == LF_ONLY) {
-        lf_av = lf_max = SumAdc(ADC_CHAN_LF, 32) >> 5;
+        lf_av = lf_max = AvgAdc(ADC_CHAN_LF);
         Dbprintf("LF 125/134kHz Baseline: %dmV", (MAX_ADC_LF_VOLTAGE * lf_av) >> 10);
         lf_baseline = lf_av;
     }
@@ -549,9 +552,9 @@ void ListenReaderField(uint8_t limit) {
 
 #if defined RDV4
         // iceman,  useless,  since we are measuring readerfield,  not our field.  My tests shows a max of 20v from a reader.
-        hf_av = hf_max = SumAdc(ADC_CHAN_HF_RDV40, 32) >> 5;
+        hf_av = hf_max = AvgAdc(ADC_CHAN_HF_RDV40);
 #else
-        hf_av = hf_max = SumAdc(ADC_CHAN_HF, 32) >> 5;
+        hf_av = hf_max = AvgAdc(ADC_CHAN_HF);
 #endif
         Dbprintf("HF 13.56MHz Baseline: %dmV", (MAX_ADC_HF_VOLTAGE * hf_av) >> 10);
         hf_baseline = hf_av;
@@ -585,7 +588,7 @@ void ListenReaderField(uint8_t limit) {
                     LED_D_OFF();
             }
 
-            lf_av_new = SumAdc(ADC_CHAN_LF, 32) >> 5;
+            lf_av_new = AvgAdc(ADC_CHAN_LF);
             // see if there's a significant change
             if (ABS(lf_av - lf_av_new) > REPORT_CHANGE) {
                 Dbprintf("LF 125/134kHz Field Change: %5dmV", (MAX_ADC_LF_VOLTAGE * lf_av_new) >> 10);
@@ -604,9 +607,9 @@ void ListenReaderField(uint8_t limit) {
             }
 
 #if defined RDV4
-            hf_av_new = SumAdc(ADC_CHAN_HF_RDV40, 32) >> 5;
+            hf_av_new = AvgAdc(ADC_CHAN_HF_RDV40);
 #else
-            hf_av_new = SumAdc(ADC_CHAN_HF, 32) >> 5;
+            hf_av_new = AvgAdc(ADC_CHAN_HF);
 #endif
             // see if there's a significant change
             if (ABS(hf_av - hf_av_new) > REPORT_CHANGE) {
diff --git a/armsrc/appmain.h b/armsrc/appmain.h
index 15f3d5ffd..6a650f163 100644
--- a/armsrc/appmain.h
+++ b/armsrc/appmain.h
@@ -30,6 +30,7 @@ void send_wtx(uint16_t wtx);
 void ReadMem(int addr);
 void __attribute__((noreturn)) AppMain(void);
 
+uint16_t AvgAdc(int ch);
 uint16_t SumAdc(int ch, int NbSamples);
 
 //void PrintToSendBuffer(void);
diff --git a/armsrc/thinfilm.c b/armsrc/thinfilm.c
index 14dd1155a..a77a70744 100644
--- a/armsrc/thinfilm.c
+++ b/armsrc/thinfilm.c
@@ -53,9 +53,9 @@ static uint16_t FpgaSendQueueDelay;
 
 static uint16_t ReadReaderField(void) {
 #if defined RDV4
-    return SumAdc(ADC_CHAN_HF_RDV40, 32) >> 5;
+    return AvgAdc(ADC_CHAN_HF_RDV40);
 #else
-    return SumAdc(ADC_CHAN_HF, 32) >> 5;
+    return AvgAdc(ADC_CHAN_HF);
 #endif
 }