Here is an example of using the PRUSS cycle counter to time a pulse. Files at: github.org/jstampfl/Prutimer
here is the PRUSS code: / pt.p // To get the echo pulse on pin P8 15. // assemble: pasm -v3 -b pt.p (could be pasm_2 if you follow directions .setcallreg r29.w0 // Going to use r31 for interrupt .origin 0 .entrypoint T811 #define CTRL 0x22000 //Start of control registers. T811: mov r8,CTRL //set r8 for the lbbo ldi r12, 0 // Local memory address for pru0 data memory ldi r2, 0 // zero to zero the cycle counter TB1: qbbs TB1,r31,15 // wait here for echo line to go low // WAIT FOR THE ECHO PULSE TB2: qbbc TB2,r31,15 // wait here for echo line to go high - start of pulse // START THE CYCLE COUNTER lbbo r9,r8,0,4 // Get the control register set r9,3 // Set the cycle counter enable sbbo r9,r8,0,4 // Put back to the register to start // WAIT FOR THE PULSE TO END TB3: qbbs TB3,r31,15 // wait here until echo line goes low. // STOP THE CYCLE COUNTER lbbo r9,r8,0,4 // get control register clr r9,3 // clear counter to disable sbbo r9,r8,0,4 // put back ldi r10,1 // not neccessary, was going to use as signal // GET THE CYCLE COUNT AND PUT IN PRU0 LOCAL DATA MEMORY lbbo r11,r8,12,4 // get the CYCLE count sbbo r10,r12,0,8 // put r10 & r11 (the unused signal & cycle count) in // pru0 data memory sbbo r2,r8,12,4 // Zero the cycle count // SEND INTERRUPT SIGNAL TO LINUX SIDE mov r31.b0,35 //Send interrupt to Linux side lbbo r11,r12,8,4 // Check for end flag from Linux side qbne TB1,r11,2 // go back for more TB4: halt -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
