fix: 32bit tick timer based on TC0 and TC1 (#653)

[proxmark3-svn] / armsrc / util.c

diff --git a/armsrc/util.c b/armsrc/util.c
index 59dfe07b45987250ae74b0495de38636e293560d..8a8d66576d4172e2611bf5d156bb340ce4087c58 100644 (file)
--- a/armsrc/util.c
+++ b/armsrc/util.c
@@ -448,31 +448,52 @@ uint32_t RAMFUNC GetCountSspClk(){
 
 
 //  -------------------------------------------------------------------------
-//  Timer for bitbanging,  or LF stuff when you need a very precis timer
+//  Timer for bitbanging, or LF stuff when you need a very precis timer
 //  1us = 1.5ticks
 //  -------------------------------------------------------------------------
 void StartTicks(void){
-       //initialization of the timer
-       // tc1 is higher 0xFFFF0000
-       // tc0 is lower 0x0000FFFF
+       // initialization of the timer
        AT91C_BASE_PMC->PMC_PCER |= (1 << AT91C_ID_TC0) | (1 << AT91C_ID_TC1);
        AT91C_BASE_TCB->TCB_BMR = AT91C_TCB_TC0XC0S_NONE | AT91C_TCB_TC1XC1S_TIOA0 | AT91C_TCB_TC2XC2S_NONE;
+
+       // disable TC0 and TC1 for re-configuration
        AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
+       AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
+
+       // first configure TC1 (higher, 0xFFFF0000) 16 bit counter
+       AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_XC1; // just connect to TIOA0 from TC0
+       AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG; // re-enable timer and wait for TC0
+
+       // second configure TC0 (lower, 0x0000FFFF) 16 bit counter
        AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV3_CLOCK | // MCK(48MHz) / 32 
-                                                               AT91C_TC_WAVE | AT91C_TC_WAVESEL_UP_AUTO | AT91C_TC_ACPA_CLEAR |
-                                                               AT91C_TC_ACPC_SET | AT91C_TC_ASWTRG_SET;
-       AT91C_BASE_TC0->TC_RA = 1;
-       AT91C_BASE_TC0->TC_RC = 0; 
+                                AT91C_TC_WAVE | AT91C_TC_WAVESEL_UP_AUTO |
+                                AT91C_TC_ACPA_CLEAR | // RA comperator clears TIOA (carry bit)
+                                AT91C_TC_ACPC_SET |   // RC comperator sets TIOA (carry bit)
+                                AT91C_TC_ASWTRG_SET;  // SWTriger sets TIOA (carry bit)
+       AT91C_BASE_TC0->TC_RC  = 0; // set TIOA (carry bit) on overflow, return to zero
+       AT91C_BASE_TC0->TC_RA  = 1; // clear carry bit on next clock cycle
+       AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG; // reset and re-enable timer
+
+       // synchronized startup procedure
+       while (AT91C_BASE_TC0->TC_CV > 0); // wait until TC0 returned to zero
+       while (AT91C_BASE_TC0->TC_CV < 2); // and has started (TC_CV > TC_RA, now TC1 is cleared)
+
+       // return to zero
+       AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG;
+       AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
+       while (AT91C_BASE_TC0->TC_CV > 0);
+}
 
-       AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;       // timer disable  
-       AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_XC1; // from TC0
-       
-       AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-       AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-       AT91C_BASE_TCB->TCB_BCR = 1;
-       
-       // wait until timer becomes zero.
-       while (AT91C_BASE_TC1->TC_CV > 0);
+
+uint32_t GetTicks(void) {
+       uint32_t hi, lo;
+
+       do {
+               hi = AT91C_BASE_TC1->TC_CV;
+               lo = AT91C_BASE_TC0->TC_CV;
+       } while(hi != AT91C_BASE_TC1->TC_CV);
+
+       return (hi << 16) | lo;
 }
 
 
@@ -480,30 +501,28 @@ void StartTicks(void){
 // if called with a high number, this will trigger the WDT...
 void WaitTicks(uint32_t ticks){
        if ( ticks == 0 ) return;
-       ticks += GET_TICKS;     
-       while (GET_TICKS < ticks);
+       ticks += GetTicks();
+       while (GetTicks() < ticks);
 }
 
 
 // Wait / Spindelay in us (microseconds) 
 // 1us = 1.5ticks.
 void WaitUS(uint16_t us){
-       if ( us == 0 ) return;
        WaitTicks( (uint32_t)us * 3 / 2 ) ;
 }
 
 
 void WaitMS(uint16_t ms){
-       if (ms == 0) return;
        WaitTicks( (uint32_t)ms * 1500 );
 }
 
 
 // Starts Clock and waits until its reset
 void ResetTicks(void){
-       AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
        AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
-       while (AT91C_BASE_TC1->TC_CV > 0);
+       AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
+       while (AT91C_BASE_TC0->TC_CV > 0);
 }