Tomás Vega / Adafruit_NeoPixel Featured

Important changes to repositories hosted on mbed.com

Mbed hosted mercurial repositories are deprecated and are due to be permanently deleted in July 2026.

To keep a copy of this software download the repository Zip archive or clone locally using Mercurial.

It is also possible to export all your personal repositories from the account settings page.

Dependents:   idd_hw3 idd_fa15_hw3_lauren_bill_tomas idd_fa15_hw3_lauren_bill_tomas Raiden ... more

Fork of PololuLedStrip by David Grayson

PololuLedStrip.cpp@16:eaed541b08b0, 2013-03-01 (annotated)

Committer:
DavidEGrayson
Date:
Fri Mar 01 05:09:55 2013 +0000
Revision:
16:eaed541b08b0
Parent:
15:d69eebdee025
Child:
17:91fb934a2166
Fine tuned the fudge factors for the M3 at 96 MHz again.  I'm not sure why they were not well tuned.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
DavidEGrayson 1:102307d9b701 1 #include "PololuLedStrip.h"
DavidEGrayson 1:102307d9b701 2
DavidEGrayson 1:102307d9b701 3 bool PololuLedStrip::interruptFriendly = false;
DavidEGrayson 1:102307d9b701 4
DavidEGrayson 15:d69eebdee025 5 // The three timed delays, in units of half-cycles.
DavidEGrayson 7:9a088f042ee0 6 uint8_t led_strip_write_delays[3];
DavidEGrayson 4:d3b60bd43811 7
DavidEGrayson 7:9a088f042ee0 8 void PololuLedStrip::calculateDelays()
DavidEGrayson 7:9a088f042ee0 9 {
DavidEGrayson 15:d69eebdee025 10 int f_mhz = SystemCoreClock / 1000000; // Clock frequency in MHz.
DavidEGrayson 14:672baf3cf941 11
DavidEGrayson 14:672baf3cf941 12 if (f_mhz <= 48)
DavidEGrayson 14:672baf3cf941 13 {
DavidEGrayson 14:672baf3cf941 14 // The delays below result in 800/1590 ns pulses and a 2500 ns period on the mbed NXP LPC11U24.
DavidEGrayson 14:672baf3cf941 15 led_strip_write_delays[0] = 0;
DavidEGrayson 14:672baf3cf941 16 led_strip_write_delays[1] = 0;
DavidEGrayson 15:d69eebdee025 17 led_strip_write_delays[2] = 5;
DavidEGrayson 14:672baf3cf941 18 }
DavidEGrayson 14:672baf3cf941 19 else
DavidEGrayson 14:672baf3cf941 20 {
DavidEGrayson 15:d69eebdee025 21 // Try to generally compute what the delays should be for a ide range of clock frequencies.
DavidEGrayson 14:672baf3cf941 22
DavidEGrayson 14:672baf3cf941 23 // The fudge factors below were experimentally chosen so that we would have
DavidEGrayson 15:d69eebdee025 24 // 700/1300 ns pulses and a ~2500 ns period on the mbed NXP LPC1768 (96 MHz Cortex-M3).
DavidEGrayson 14:672baf3cf941 25 // If you ever change these numbers, it is important to check the the subtractions below
DavidEGrayson 15:d69eebdee025 26 // will not overflow in the worst case, which is f_mhz = 49.
DavidEGrayson 15:d69eebdee025 27 led_strip_write_delays[0] = 700*f_mhz/1000 - 23;
DavidEGrayson 16:eaed541b08b0 28 led_strip_write_delays[1] = 600*f_mhz/1000 - 18;
DavidEGrayson 16:eaed541b08b0 29 led_strip_write_delays[2] = 1200*f_mhz/1000 - 33;
DavidEGrayson 15:d69eebdee025 30 }
DavidEGrayson 15:d69eebdee025 31
DavidEGrayson 15:d69eebdee025 32 // Convert from units of cycles to units of half-cycles; it makes the assembly faster.
DavidEGrayson 15:d69eebdee025 33 for(int i = 0; i < 3; i++)
DavidEGrayson 15:d69eebdee025 34 {
DavidEGrayson 15:d69eebdee025 35 led_strip_write_delays[i] <<= 1;
DavidEGrayson 12:b6df8ac053c8 36 }
DavidEGrayson 7:9a088f042ee0 37 }
DavidEGrayson 6:9d0530b7dae2 38
DavidEGrayson 1:102307d9b701 39 PololuLedStrip::PololuLedStrip(PinName pinName)
DavidEGrayson 1:102307d9b701 40 {
DavidEGrayson 1:102307d9b701 41 gpio_init(&gpio, pinName, PIN_OUTPUT);
DavidEGrayson 1:102307d9b701 42 }
DavidEGrayson 1:102307d9b701 43
DavidEGrayson 1:102307d9b701 44 void PololuLedStrip::write(rgb_color * colors, unsigned int count)
DavidEGrayson 1:102307d9b701 45 {
DavidEGrayson 8:1578776ceac5 46 calculateDelays();
DavidEGrayson 8:1578776ceac5 47
DavidEGrayson 1:102307d9b701 48 __disable_irq(); // Disable interrupts temporarily because we don't want our pulse timing to be messed up.
DavidEGrayson 7:9a088f042ee0 49
DavidEGrayson 1:102307d9b701 50 while(count--)
DavidEGrayson 1:102307d9b701 51 {
DavidEGrayson 9:6ffb85d69eaf 52 led_strip_write_color(colors, gpio.reg_set, gpio.reg_clr, gpio.mask);
DavidEGrayson 9:6ffb85d69eaf 53 colors++;
DavidEGrayson 9:6ffb85d69eaf 54
DavidEGrayson 1:102307d9b701 55 if (interruptFriendly)
DavidEGrayson 1:102307d9b701 56 {
DavidEGrayson 1:102307d9b701 57 __enable_irq();
DavidEGrayson 1:102307d9b701 58 __nop();
DavidEGrayson 1:102307d9b701 59 __nop();
DavidEGrayson 1:102307d9b701 60 __nop();
DavidEGrayson 1:102307d9b701 61 __disable_irq();
DavidEGrayson 1:102307d9b701 62 }
DavidEGrayson 1:102307d9b701 63 }
DavidEGrayson 1:102307d9b701 64
DavidEGrayson 1:102307d9b701 65 __enable_irq(); // Re-enable interrupts now that we are done.
DavidEGrayson 1:102307d9b701 66 wait_us(24); // Hold the line low for 24 microseconds to send the reset signal.
DavidEGrayson 9:6ffb85d69eaf 67
DavidEGrayson 9:6ffb85d69eaf 68 //*(gpio.reg_set) = gpio.mask;
DavidEGrayson 9:6ffb85d69eaf 69 //*(gpio.reg_clr) = gpio.mask;
DavidEGrayson 9:6ffb85d69eaf 70
DavidEGrayson 1:102307d9b701 71 }