From 0c54d13c47b4a3d6ddc8ef8f93bec3b881237c50 Mon Sep 17 00:00:00 2001
From: iceman1001 <iceman@iuse.se>
Date: Fri, 9 Oct 2020 14:30:34 +0200
Subject: [PATCH] added a precision timer ( 0.6ns for 43ms)

---
 armsrc/ticks.c | 25 +++++++++++++++++++++++++
 armsrc/ticks.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/armsrc/ticks.c b/armsrc/ticks.c
index e8ac13f89..9b563cc54 100644
--- a/armsrc/ticks.c
+++ b/armsrc/ticks.c
@@ -13,6 +13,31 @@
 #include "proxmark3_arm.h"
 #include "dbprint.h"
 
+
+// timer counts in 666ns increments (32/48MHz), rounding applies
+// WARNING: timer can't measure more than 43ms (666ns * 0xFFFF)
+void SpinDelayUsPrecision(int us) {
+    int ticks = ((MCK / 1000000) * us + 16) >> 5;
+
+    // Borrow a PWM unit for my real-time clock
+    AT91C_BASE_PWMC->PWMC_ENA = PWM_CHANNEL(0);
+
+    // 48 MHz / 32 gives 1.5 Mhz
+    AT91C_BASE_PWMC_CH0->PWMC_CMR = PWM_CH_MODE_PRESCALER(5);      // Channel Mode Register
+    AT91C_BASE_PWMC_CH0->PWMC_CDTYR = 0;                           // Channel Duty Cycle Register
+    AT91C_BASE_PWMC_CH0->PWMC_CPRDR = 0xFFFF;                      // Channel Period Register
+
+    uint16_t start = AT91C_BASE_PWMC_CH0->PWMC_CCNTR;
+
+    for (;;) {
+        uint16_t now = AT91C_BASE_PWMC_CH0->PWMC_CCNTR;
+        if (now == (uint16_t)(start + ticks))
+            return;
+
+        WDT_HIT();
+    }
+}
+
 // timer counts in 21.3us increments (1024/48MHz), rounding applies
 // WARNING: timer can't measure more than 1.39s (21.3us * 0xffff)
 void SpinDelayUs(int us) {
diff --git a/armsrc/ticks.h b/armsrc/ticks.h
index 9d8d178d5..dcf23ece1 100644
--- a/armsrc/ticks.h
+++ b/armsrc/ticks.h
@@ -20,6 +20,7 @@
 
 void SpinDelay(int ms);
 void SpinDelayUs(int us);
+void SpinDelayUsPrecision(int us);  // precision 0.6us , running for 43ms before 
 
 void StartTickCount(void);
 uint32_t RAMFUNC GetTickCount(void);