school project using led strip
Fork of PololuLedStrip by
PololuLedStrip.cpp
- Committer:
- DavidEGrayson
- Date:
- 2013-10-09
- Revision:
- 19:46d7ab0ba3e7
- Parent:
- 17:91fb934a2166
- Child:
- 22:8dc878594d24
- Child:
- 23:5368af3ff07d
File content as of revision 19:46d7ab0ba3e7:
#include "PololuLedStrip.h" bool PololuLedStrip::interruptFriendly = false; // The two timed delays, in units of half-cycles. uint8_t led_strip_write_delays[2]; void PololuLedStrip::calculateDelays() { int f_mhz = SystemCoreClock / 1000000; // Clock frequency in MHz. if (f_mhz <= 48) { // The delays below result in 360/1120 ns pulses and a 1880 ns period on the mbed NXP LPC11U24. led_strip_write_delays[0] = 0; led_strip_write_delays[1] = 0; } else { // Try to generally compute what the delays should be for a ide range of clock frequencies. // The fudge factors below were experimentally chosen so that we would have // ~100/840 ns pulses and a ~1430 ns period on the mbed NXP LPC1768 (96 MHz Cortex-M3). // There seem to be some ~100 ns inconsistencies in the timing depending on which example program is // running; the most likely explanation is some kind of flash caching that affects the timing. // If you ever change these numbers, it is important to check the the subtractions below // will not overflow in the worst case (smallest possible f_mhz). led_strip_write_delays[0] = 750*f_mhz/1000 - 33; led_strip_write_delays[1] = 550*f_mhz/1000 - 20; } // Convert from units of cycles to units of half-cycles; it makes the assembly faster. for(int i = 0; i < 2; i++) { led_strip_write_delays[i] <<= 1; } } PololuLedStrip::PololuLedStrip(PinName pinName) { gpio_init(&gpio, pinName, PIN_OUTPUT); } void PololuLedStrip::write(rgb_color * colors, unsigned int count) { calculateDelays(); __disable_irq(); // Disable interrupts temporarily because we don't want our pulse timing to be messed up. while(count--) { led_strip_write_color(colors, gpio.reg_set, gpio.reg_clr, gpio.mask); colors++; if (interruptFriendly) { __enable_irq(); __nop(); __nop(); __nop(); __disable_irq(); } } __enable_irq(); // Re-enable interrupts now that we are done. wait_us(24); // Hold the line low for 24 microseconds to send the reset signal. //*(gpio.reg_set) = gpio.mask; //*(gpio.reg_clr) = gpio.mask; }