X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/9783989b400be4ed19cbf12defa4d6dbcdcd9fc8..5ee53a0e75c48de359108f5d21d4b829ed504467:/armsrc/util.c?ds=sidebyside

diff --git a/armsrc/util.c b/armsrc/util.c
index 8576ddce..3d536f39 100644
--- a/armsrc/util.c
+++ b/armsrc/util.c
@@ -304,11 +304,12 @@ void FormatVersionInformation(char *dst, int len, const char *prefix, void *vers
 
 void StartTickCount()
 {
-//  must be 0x40, but on my cpu - included divider is optimal
-//  0x20 - 1 ms / bit 
-//  0x40 - 2 ms / bit
-
-	AT91C_BASE_RTTC->RTTC_RTMR = AT91C_RTTC_RTTRST + 0x001D; // was 0x003B
+	// This timer is based on the slow clock. The slow clock frequency is between 22kHz and 40kHz.
+	// We can determine the actual slow clock frequency by looking at the Main Clock Frequency Register.
+    uint16_t mainf = AT91C_BASE_PMC->PMC_MCFR & 0xffff;		// = 16 * main clock frequency (16MHz) / slow clock frequency
+	// set RealTimeCounter divider to count at 1kHz:
+	AT91C_BASE_RTTC->RTTC_RTMR = AT91C_RTTC_RTTRST | ((256000 + (mainf/2)) / mainf);
+	// note: worst case precision is approx 2.5%
 }
 
 /*
@@ -344,7 +345,9 @@ void StartCountUS()
 	}
 
 uint32_t RAMFUNC GetCountUS(){
-	return (AT91C_BASE_TC1->TC_CV * 0x8000) + ((AT91C_BASE_TC0->TC_CV / 15) * 10);
+	//return (AT91C_BASE_TC1->TC_CV * 0x8000) + ((AT91C_BASE_TC0->TC_CV / 15) * 10);
+	//  By suggestion from PwPiwi, http://www.proxmark.org/forum/viewtopic.php?pid=17548#p17548
+	return (AT91C_BASE_TC1->TC_CV * 0x8000) + ((AT91C_BASE_TC0->TC_CV * 2) / 3); 
 }
 
 static uint32_t GlobalUsCounter = 0;