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

led_strip_write_color.s@27:9a62663f3de2, 2018-05-19 (annotated)

Committer:
thegink
Date:
Sat May 19 14:16:38 2018 +0000
Revision:
27:9a62663f3de2
Parent:
24:5c01a6fa1556 
Added #define for RGB/GRB order for WS2811 and WS2812b based strips, respectively. Ideally this should be selectable per instance, but it's late, and I'm tired.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
DavidEGrayson 0:06475317f283 1 AREA asm_func, CODE, READONLY
DavidEGrayson 0:06475317f283 2 EXPORT led_strip_write_color
DavidEGrayson 6:9d0530b7dae2 3 IMPORT led_strip_write_delays
DavidEGrayson 0:06475317f283 4
DavidEGrayson 7:9a088f042ee0 5 MACRO
DavidEGrayson 7:9a088f042ee0 6 delay $id
DavidEGrayson 7:9a088f042ee0 7 ldr r5, =led_strip_write_delays
DavidEGrayson 7:9a088f042ee0 8 ldrb r5, [r5, $id]
DavidEGrayson 7:9a088f042ee0 9 ldr r4, =delay_region_end
DavidEGrayson 9:6ffb85d69eaf 10 subs r4, r4, r5
DavidEGrayson 7:9a088f042ee0 11 blx r4
DavidEGrayson 7:9a088f042ee0 12 MEND
DavidEGrayson 7:9a088f042ee0 13
DavidEGrayson 0:06475317f283 14 led_strip_write_color
DavidEGrayson 5:690fdfb595de 15 ; Register usage:
DavidEGrayson 5:690fdfb595de 16 ; These are the first 4 arguments to the method:
DavidEGrayson 5:690fdfb595de 17 ; R0: pointer to the color to send
DavidEGrayson 5:690fdfb595de 18 ; R1: pointer to the register for setting the pin
DavidEGrayson 5:690fdfb595de 19 ; R2: pointer to the register for clearing the pin
DavidEGrayson 5:690fdfb595de 20 ; R3: pin mask
DavidEGrayson 5:690fdfb595de 21 ; Additionally, we use these registers:
DavidEGrayson 5:690fdfb595de 22 ; R4: temporary register
DavidEGrayson 6:9d0530b7dae2 23 ; R5: temporary register
DavidEGrayson 20:656bbcb64e3b 24 ; R6: shift register that holds the 24-bit color
DavidEGrayson 5:690fdfb595de 25 ; R7: the number of bits we still need to send
DavidEGrayson 5:690fdfb595de 26 ; R13: Link Register, holds return addresses.
DavidEGrayson 7:9a088f042ee0 27
DavidEGrayson 9:6ffb85d69eaf 28 ; Push those registers so we can restore them later.
DavidEGrayson 11:e00ba70ac54c 29 push {r4, r5, r6, r7, lr}
DavidEGrayson 10:f1bb84b97788 30
thegink 27:9a62663f3de2 31 ldrb r6, [r0, #0] ; Load first colour.
thegink 27:9a62663f3de2 32 lsls r6, r6, #24 ; Put first colour in MSB of r6.
thegink 27:9a62663f3de2 33 ldrb r4, [r0, #1] ; Load second colour.
DavidEGrayson 9:6ffb85d69eaf 34 lsls r4, r4, #16
thegink 27:9a62663f3de2 35 orrs r6, r6, r4 ; Put second colour in r6.
thegink 27:9a62663f3de2 36 ldrb r4, [r0, #2] ; Load third colour.
DavidEGrayson 9:6ffb85d69eaf 37 lsls r4, r4, #8
thegink 27:9a62663f3de2 38 orrs r6, r6, r4 ; Put third colour in r6.
DavidEGrayson 9:6ffb85d69eaf 39
DavidEGrayson 21:87fd6273e0ff 40 ; On the Cortex-M3 we simply did:
DavidEGrayson 9:6ffb85d69eaf 41 ; ldr r6, [r0] ; Read the color. Now we have: xxBbGgRr
DavidEGrayson 9:6ffb85d69eaf 42 ; rbit r6, r6 ; Reverse the order of the bits: rRgGbBxx
DavidEGrayson 9:6ffb85d69eaf 43 ; rev r6, r6 ; Reverse the order of the bytes: xxbBgGrR
DavidEGrayson 9:6ffb85d69eaf 44 ; and then we used rrxs for shifting to the right through carry.
DavidEGrayson 9:6ffb85d69eaf 45
DavidEGrayson 9:6ffb85d69eaf 46 ldr r7, =24 ; Initialize the loop counter register.
DavidEGrayson 0:06475317f283 47
DavidEGrayson 0:06475317f283 48 send_led_strip_bit
DavidEGrayson 0:06475317f283 49 str r3, [r1] ; Drive the line high.
DavidEGrayson 0:06475317f283 50
DavidEGrayson 19:46d7ab0ba3e7 51 ; It doesn't really matter exactly how long we delay here as long as it is
DavidEGrayson 24:5c01a6fa1556 52 ; less than the LED's threshold between 0 and 1.
DavidEGrayson 19:46d7ab0ba3e7 53 nop
DavidEGrayson 19:46d7ab0ba3e7 54 nop
DavidEGrayson 19:46d7ab0ba3e7 55 nop
DavidEGrayson 19:46d7ab0ba3e7 56 nop
DavidEGrayson 19:46d7ab0ba3e7 57 nop
DavidEGrayson 19:46d7ab0ba3e7 58 nop
DavidEGrayson 0:06475317f283 59
DavidEGrayson 9:6ffb85d69eaf 60 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 61 tst r6, r4
DavidEGrayson 19:46d7ab0ba3e7 62 bne delay0
DavidEGrayson 12:b6df8ac053c8 63 str r3, [r2] ; If the bit to send it 0, drive the line low.
DavidEGrayson 24:5c01a6fa1556 64
DavidEGrayson 19:46d7ab0ba3e7 65 delay0
DavidEGrayson 19:46d7ab0ba3e7 66 delay #0
DavidEGrayson 0:06475317f283 67
DavidEGrayson 9:6ffb85d69eaf 68 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 69 tst r6, r4
DavidEGrayson 19:46d7ab0ba3e7 70 beq delay1
DavidEGrayson 12:b6df8ac053c8 71 str r3, [r2] ; If the bit to send is 1, drive the line low.
DavidEGrayson 24:5c01a6fa1556 72
DavidEGrayson 19:46d7ab0ba3e7 73 delay1
DavidEGrayson 19:46d7ab0ba3e7 74 delay #1
DavidEGrayson 4:d3b60bd43811 75
DavidEGrayson 12:b6df8ac053c8 76 lsls r6, r6, #1 ; Shift color bits.
DavidEGrayson 6:9d0530b7dae2 77 subs r7, r7, #1 ; Decrement the loop counter.
DavidEGrayson 12:b6df8ac053c8 78 bne send_led_strip_bit ; Send another bit if we have not reached zero.
DavidEGrayson 12:b6df8ac053c8 79 pop {r4, r5, r6, r7, pc} ; Otherwise, restore the registers and return.
DavidEGrayson 19:46d7ab0ba3e7 80 bx lr;
DavidEGrayson 4:d3b60bd43811 81
DavidEGrayson 4:d3b60bd43811 82 delay_region
DavidEGrayson 5:690fdfb595de 83 ; The following is 128 nops.
DavidEGrayson 0:06475317f283 84 nop
DavidEGrayson 0:06475317f283 85 nop
DavidEGrayson 0:06475317f283 86 nop
DavidEGrayson 0:06475317f283 87 nop
DavidEGrayson 0:06475317f283 88 nop
DavidEGrayson 0:06475317f283 89 nop
DavidEGrayson 0:06475317f283 90 nop
DavidEGrayson 0:06475317f283 91 nop
DavidEGrayson 0:06475317f283 92 nop
DavidEGrayson 0:06475317f283 93 nop
DavidEGrayson 0:06475317f283 94 nop
DavidEGrayson 0:06475317f283 95 nop
DavidEGrayson 0:06475317f283 96 nop
DavidEGrayson 4:d3b60bd43811 97 nop
DavidEGrayson 4:d3b60bd43811 98 nop
DavidEGrayson 4:d3b60bd43811 99 nop
DavidEGrayson 4:d3b60bd43811 100
DavidEGrayson 0:06475317f283 101 nop
DavidEGrayson 0:06475317f283 102 nop
DavidEGrayson 0:06475317f283 103 nop
DavidEGrayson 0:06475317f283 104 nop
DavidEGrayson 0:06475317f283 105 nop
DavidEGrayson 0:06475317f283 106 nop
DavidEGrayson 0:06475317f283 107 nop
DavidEGrayson 0:06475317f283 108 nop
DavidEGrayson 0:06475317f283 109 nop
DavidEGrayson 0:06475317f283 110 nop
DavidEGrayson 0:06475317f283 111 nop
DavidEGrayson 0:06475317f283 112 nop
DavidEGrayson 0:06475317f283 113 nop
DavidEGrayson 0:06475317f283 114 nop
DavidEGrayson 0:06475317f283 115 nop
DavidEGrayson 0:06475317f283 116 nop
DavidEGrayson 4:d3b60bd43811 117
DavidEGrayson 0:06475317f283 118 nop
DavidEGrayson 0:06475317f283 119 nop
DavidEGrayson 0:06475317f283 120 nop
DavidEGrayson 0:06475317f283 121 nop
DavidEGrayson 4:d3b60bd43811 122 nop
DavidEGrayson 4:d3b60bd43811 123 nop
DavidEGrayson 0:06475317f283 124 nop
DavidEGrayson 0:06475317f283 125 nop
DavidEGrayson 0:06475317f283 126 nop
DavidEGrayson 0:06475317f283 127 nop
DavidEGrayson 0:06475317f283 128 nop
DavidEGrayson 0:06475317f283 129 nop
DavidEGrayson 0:06475317f283 130 nop
DavidEGrayson 0:06475317f283 131 nop
DavidEGrayson 0:06475317f283 132 nop
DavidEGrayson 0:06475317f283 133 nop
DavidEGrayson 0:06475317f283 134
DavidEGrayson 0:06475317f283 135 nop
DavidEGrayson 0:06475317f283 136 nop
DavidEGrayson 0:06475317f283 137 nop
DavidEGrayson 0:06475317f283 138 nop
DavidEGrayson 0:06475317f283 139 nop
DavidEGrayson 0:06475317f283 140 nop
DavidEGrayson 0:06475317f283 141 nop
DavidEGrayson 0:06475317f283 142 nop
DavidEGrayson 0:06475317f283 143 nop
DavidEGrayson 0:06475317f283 144 nop
DavidEGrayson 4:d3b60bd43811 145 nop
DavidEGrayson 4:d3b60bd43811 146 nop
DavidEGrayson 4:d3b60bd43811 147 nop
DavidEGrayson 4:d3b60bd43811 148 nop
DavidEGrayson 4:d3b60bd43811 149 nop
DavidEGrayson 4:d3b60bd43811 150 nop
DavidEGrayson 0:06475317f283 151
DavidEGrayson 0:06475317f283 152 nop
DavidEGrayson 0:06475317f283 153 nop
DavidEGrayson 0:06475317f283 154 nop
DavidEGrayson 0:06475317f283 155 nop
DavidEGrayson 0:06475317f283 156 nop
DavidEGrayson 0:06475317f283 157 nop
DavidEGrayson 0:06475317f283 158 nop
DavidEGrayson 0:06475317f283 159 nop
DavidEGrayson 0:06475317f283 160 nop
DavidEGrayson 0:06475317f283 161 nop
DavidEGrayson 4:d3b60bd43811 162 nop
DavidEGrayson 4:d3b60bd43811 163 nop
DavidEGrayson 4:d3b60bd43811 164 nop
DavidEGrayson 4:d3b60bd43811 165 nop
DavidEGrayson 4:d3b60bd43811 166 nop
DavidEGrayson 4:d3b60bd43811 167 nop
DavidEGrayson 0:06475317f283 168
DavidEGrayson 0:06475317f283 169 nop
DavidEGrayson 0:06475317f283 170 nop
DavidEGrayson 0:06475317f283 171 nop
DavidEGrayson 0:06475317f283 172 nop
DavidEGrayson 0:06475317f283 173 nop
DavidEGrayson 0:06475317f283 174 nop
DavidEGrayson 0:06475317f283 175 nop
DavidEGrayson 0:06475317f283 176 nop
DavidEGrayson 0:06475317f283 177 nop
DavidEGrayson 0:06475317f283 178 nop
DavidEGrayson 0:06475317f283 179 nop
DavidEGrayson 0:06475317f283 180 nop
DavidEGrayson 0:06475317f283 181 nop
DavidEGrayson 0:06475317f283 182 nop
DavidEGrayson 0:06475317f283 183 nop
DavidEGrayson 0:06475317f283 184 nop
DavidEGrayson 0:06475317f283 185
DavidEGrayson 0:06475317f283 186 nop
DavidEGrayson 0:06475317f283 187 nop
DavidEGrayson 0:06475317f283 188 nop
DavidEGrayson 0:06475317f283 189 nop
DavidEGrayson 0:06475317f283 190 nop
DavidEGrayson 0:06475317f283 191 nop
DavidEGrayson 0:06475317f283 192 nop
DavidEGrayson 0:06475317f283 193 nop
DavidEGrayson 0:06475317f283 194 nop
DavidEGrayson 0:06475317f283 195 nop
DavidEGrayson 4:d3b60bd43811 196 nop
DavidEGrayson 4:d3b60bd43811 197 nop
DavidEGrayson 4:d3b60bd43811 198 nop
DavidEGrayson 4:d3b60bd43811 199 nop
DavidEGrayson 4:d3b60bd43811 200 nop
DavidEGrayson 4:d3b60bd43811 201 nop
DavidEGrayson 4:d3b60bd43811 202
DavidEGrayson 0:06475317f283 203 nop
DavidEGrayson 0:06475317f283 204 nop
DavidEGrayson 0:06475317f283 205 nop
DavidEGrayson 0:06475317f283 206 nop
DavidEGrayson 0:06475317f283 207 nop
DavidEGrayson 0:06475317f283 208 nop
DavidEGrayson 4:d3b60bd43811 209 nop
DavidEGrayson 4:d3b60bd43811 210 nop
DavidEGrayson 4:d3b60bd43811 211 nop
DavidEGrayson 4:d3b60bd43811 212 nop
DavidEGrayson 4:d3b60bd43811 213 nop
DavidEGrayson 4:d3b60bd43811 214 nop
DavidEGrayson 4:d3b60bd43811 215 nop
DavidEGrayson 4:d3b60bd43811 216 nop
DavidEGrayson 4:d3b60bd43811 217 nop
DavidEGrayson 4:d3b60bd43811 218 nop
DavidEGrayson 5:690fdfb595de 219 delay_region_end
DavidEGrayson 4:d3b60bd43811 220 bx lr ; return
DavidEGrayson 0:06475317f283 221
DavidEGrayson 0:06475317f283 222 END