David Knight / PololuLedStrip

This library lets you control the addressable RGB LED strips from Pololu Robotics. Forked to add selectable colour order (Support RGB or GRB Leds)

Fork of PololuLedStrip by David Grayson

PololuLedStrip.cpp@26:c3193bc73cff, 2017-11-01 (annotated)

Committer:
DavidEGrayson
Date:
Wed Nov 01 23:11:49 2017 +0000
Revision:
26:c3193bc73cff
Parent:
25:d72818ba17cc
Child:
27:9a62663f3de2
Make it be a compile-time error if GPIO_IP_WITHOUT_BRR is set.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
DavidEGrayson 1:102307d9b701 1 #include "PololuLedStrip.h"
DavidEGrayson 1:102307d9b701 2
DavidEGrayson 26:c3193bc73cff 3 // Our assembly code currently does not work with chip families like the STM32F4
DavidEGrayson 26:c3193bc73cff 4 // that use the same register and a different mask for setting and clearing
DavidEGrayson 26:c3193bc73cff 5 // outputs.
DavidEGrayson 26:c3193bc73cff 6 #ifdef GPIO_IP_WITHOUT_BRR
DavidEGrayson 26:c3193bc73cff 7 #error This chip is not supported: does not have separate registers for setting and clearing GPIO outputs.
DavidEGrayson 26:c3193bc73cff 8 #endif
DavidEGrayson 26:c3193bc73cff 9
DavidEGrayson 1:102307d9b701 10 bool PololuLedStrip::interruptFriendly = false;
DavidEGrayson 1:102307d9b701 11
DavidEGrayson 19:46d7ab0ba3e7 12 // The two timed delays, in units of half-cycles.
DavidEGrayson 19:46d7ab0ba3e7 13 uint8_t led_strip_write_delays[2];
DavidEGrayson 4:d3b60bd43811 14
DavidEGrayson 7:9a088f042ee0 15 void PololuLedStrip::calculateDelays()
DavidEGrayson 7:9a088f042ee0 16 {
DavidEGrayson 15:d69eebdee025 17 int f_mhz = SystemCoreClock / 1000000; // Clock frequency in MHz.
DavidEGrayson 14:672baf3cf941 18
DavidEGrayson 14:672baf3cf941 19 if (f_mhz <= 48)
DavidEGrayson 14:672baf3cf941 20 {
DavidEGrayson 19:46d7ab0ba3e7 21 // The delays below result in 360/1120 ns pulses and a 1880 ns period on the mbed NXP LPC11U24.
DavidEGrayson 14:672baf3cf941 22 led_strip_write_delays[0] = 0;
DavidEGrayson 14:672baf3cf941 23 led_strip_write_delays[1] = 0;
DavidEGrayson 14:672baf3cf941 24 }
DavidEGrayson 14:672baf3cf941 25 else
DavidEGrayson 14:672baf3cf941 26 {
DavidEGrayson 22:5368af3ff07d 27 // Try to generally compute what the delays should be for a wide range of clock frequencies.
DavidEGrayson 14:672baf3cf941 28
DavidEGrayson 14:672baf3cf941 29 // The fudge factors below were experimentally chosen so that we would have
DavidEGrayson 23:881d93b8749a 30 // ~100 ns and ~840 ns pulses and a ~1430 ns period on the mbed NXP LPC1768 (96 MHz Cortex-M3).
DavidEGrayson 17:91fb934a2166 31 // There seem to be some ~100 ns inconsistencies in the timing depending on which example program is
DavidEGrayson 17:91fb934a2166 32 // running; the most likely explanation is some kind of flash caching that affects the timing.
DavidEGrayson 14:672baf3cf941 33 // If you ever change these numbers, it is important to check the the subtractions below
DavidEGrayson 19:46d7ab0ba3e7 34 // will not overflow in the worst case (smallest possible f_mhz).
DavidEGrayson 23:881d93b8749a 35 //
DavidEGrayson 23:881d93b8749a 36 // On an STM32F303K8 (72 MHz Cortex-M4), these delays give us ~170 ns and ~840 ns pulses
DavidEGrayson 23:881d93b8749a 37 // and a ~1595 ns period, and there were no timing differences between the two
DavidEGrayson 23:881d93b8749a 38 // example programs.
DavidEGrayson 19:46d7ab0ba3e7 39 led_strip_write_delays[0] = 750*f_mhz/1000 - 33;
DavidEGrayson 19:46d7ab0ba3e7 40 led_strip_write_delays[1] = 550*f_mhz/1000 - 20;
DavidEGrayson 15:d69eebdee025 41 }
DavidEGrayson 15:d69eebdee025 42
DavidEGrayson 15:d69eebdee025 43 // Convert from units of cycles to units of half-cycles; it makes the assembly faster.
DavidEGrayson 22:5368af3ff07d 44 led_strip_write_delays[0] <<= 1;
DavidEGrayson 22:5368af3ff07d 45 led_strip_write_delays[1] <<= 1;
DavidEGrayson 7:9a088f042ee0 46 }
DavidEGrayson 6:9d0530b7dae2 47
DavidEGrayson 1:102307d9b701 48 PololuLedStrip::PololuLedStrip(PinName pinName)
DavidEGrayson 1:102307d9b701 49 {
DavidEGrayson 22:5368af3ff07d 50 gpio_init_out(&gpio, pinName);
DavidEGrayson 1:102307d9b701 51 }
DavidEGrayson 1:102307d9b701 52
DavidEGrayson 1:102307d9b701 53 void PololuLedStrip::write(rgb_color * colors, unsigned int count)
DavidEGrayson 1:102307d9b701 54 {
DavidEGrayson 8:1578776ceac5 55 calculateDelays();
DavidEGrayson 8:1578776ceac5 56
DavidEGrayson 1:102307d9b701 57 __disable_irq(); // Disable interrupts temporarily because we don't want our pulse timing to be messed up.
DavidEGrayson 7:9a088f042ee0 58
DavidEGrayson 1:102307d9b701 59 while(count--)
DavidEGrayson 1:102307d9b701 60 {
DavidEGrayson 9:6ffb85d69eaf 61 led_strip_write_color(colors, gpio.reg_set, gpio.reg_clr, gpio.mask);
DavidEGrayson 9:6ffb85d69eaf 62 colors++;
DavidEGrayson 9:6ffb85d69eaf 63
DavidEGrayson 1:102307d9b701 64 if (interruptFriendly)
DavidEGrayson 1:102307d9b701 65 {
DavidEGrayson 1:102307d9b701 66 __enable_irq();
DavidEGrayson 1:102307d9b701 67 __nop();
DavidEGrayson 1:102307d9b701 68 __nop();
DavidEGrayson 1:102307d9b701 69 __nop();
DavidEGrayson 1:102307d9b701 70 __disable_irq();
DavidEGrayson 1:102307d9b701 71 }
DavidEGrayson 1:102307d9b701 72 }
DavidEGrayson 1:102307d9b701 73
DavidEGrayson 1:102307d9b701 74 __enable_irq(); // Re-enable interrupts now that we are done.
DavidEGrayson 25:d72818ba17cc 75 wait_us(80); // Send the reset signal.
DavidEGrayson 1:102307d9b701 76 }