yan xu / PololuLedStrip

WS2812B

Dependents:   high speed light Bracelet

Fork of PololuLedStrip by David Grayson

led_strip_write_color.s@19:46d7ab0ba3e7, 2013-10-09 (annotated)

Committer:
DavidEGrayson
Date:
Wed Oct 09 01:13:49 2013 +0000
Revision:
19:46d7ab0ba3e7
Parent:
12:b6df8ac053c8
Child:
20:656bbcb64e3b
Changed the timing so that this library only supports the high-speed strips now.

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 8:1578776ceac5 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
DavidEGrayson 9:6ffb85d69eaf 31 ldrb r4, [r0, #0] ; Load red.
DavidEGrayson 9:6ffb85d69eaf 32 lsls r4, r4, #24
DavidEGrayson 9:6ffb85d69eaf 33 mov r6, r4 ; Put red in MSB of r6.
DavidEGrayson 9:6ffb85d69eaf 34 ldrb r4, [r0, #1] ; Load green.
DavidEGrayson 9:6ffb85d69eaf 35 lsls r4, r4, #16
DavidEGrayson 10:f1bb84b97788 36 orrs r6, r6, r4 ; Put green in r6.
DavidEGrayson 9:6ffb85d69eaf 37 ldrb r4, [r0, #2] ; Load blue.
DavidEGrayson 9:6ffb85d69eaf 38 lsls r4, r4, #8
DavidEGrayson 10:f1bb84b97788 39 orrs r6, r6, r4 ; Put blue in MSB of r6.
DavidEGrayson 9:6ffb85d69eaf 40
DavidEGrayson 9:6ffb85d69eaf 41 ; On the Cortex M0 we simply did:
DavidEGrayson 9:6ffb85d69eaf 42 ; ldr r6, [r0] ; Read the color. Now we have: xxBbGgRr
DavidEGrayson 9:6ffb85d69eaf 43 ; rbit r6, r6 ; Reverse the order of the bits: rRgGbBxx
DavidEGrayson 9:6ffb85d69eaf 44 ; rev r6, r6 ; Reverse the order of the bytes: xxbBgGrR
DavidEGrayson 9:6ffb85d69eaf 45 ; and then we used rrxs for shifting to the right through carry.
DavidEGrayson 9:6ffb85d69eaf 46
DavidEGrayson 9:6ffb85d69eaf 47 ldr r7, =24 ; Initialize the loop counter register.
DavidEGrayson 0:06475317f283 48
DavidEGrayson 0:06475317f283 49 send_led_strip_bit
DavidEGrayson 0:06475317f283 50 str r3, [r1] ; Drive the line high.
DavidEGrayson 0:06475317f283 51
DavidEGrayson 19:46d7ab0ba3e7 52 ; It doesn't really matter exactly how long we delay here as long as it is
DavidEGrayson 19:46d7ab0ba3e7 53 ; less than 540 microseconds.
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 19:46d7ab0ba3e7 59 nop
DavidEGrayson 0:06475317f283 60
DavidEGrayson 9:6ffb85d69eaf 61 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 62 tst r6, r4
DavidEGrayson 19:46d7ab0ba3e7 63 bne delay0
DavidEGrayson 12:b6df8ac053c8 64 str r3, [r2] ; If the bit to send it 0, drive the line low.
DavidEGrayson 19:46d7ab0ba3e7 65 delay0
DavidEGrayson 0:06475317f283 66
DavidEGrayson 19:46d7ab0ba3e7 67 delay #0
DavidEGrayson 0:06475317f283 68
DavidEGrayson 9:6ffb85d69eaf 69 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 70 tst r6, r4
DavidEGrayson 19:46d7ab0ba3e7 71 beq delay1
DavidEGrayson 12:b6df8ac053c8 72 str r3, [r2] ; If the bit to send is 1, drive the line low.
DavidEGrayson 19:46d7ab0ba3e7 73 delay1
DavidEGrayson 0:06475317f283 74
DavidEGrayson 19:46d7ab0ba3e7 75 delay #1
DavidEGrayson 4:d3b60bd43811 76
DavidEGrayson 12:b6df8ac053c8 77 lsls r6, r6, #1 ; Shift color bits.
DavidEGrayson 6:9d0530b7dae2 78 subs r7, r7, #1 ; Decrement the loop counter.
DavidEGrayson 12:b6df8ac053c8 79 bne send_led_strip_bit ; Send another bit if we have not reached zero.
DavidEGrayson 12:b6df8ac053c8 80 pop {r4, r5, r6, r7, pc} ; Otherwise, restore the registers and return.
DavidEGrayson 19:46d7ab0ba3e7 81 bx lr;
DavidEGrayson 4:d3b60bd43811 82
DavidEGrayson 4:d3b60bd43811 83 delay_region
DavidEGrayson 5:690fdfb595de 84 ; The following is 128 nops.
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 0:06475317f283 97 nop
DavidEGrayson 4:d3b60bd43811 98 nop
DavidEGrayson 4:d3b60bd43811 99 nop
DavidEGrayson 4:d3b60bd43811 100 nop
DavidEGrayson 4:d3b60bd43811 101
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 0:06475317f283 117 nop
DavidEGrayson 4:d3b60bd43811 118
DavidEGrayson 0:06475317f283 119 nop
DavidEGrayson 0:06475317f283 120 nop
DavidEGrayson 0:06475317f283 121 nop
DavidEGrayson 0:06475317f283 122 nop
DavidEGrayson 4:d3b60bd43811 123 nop
DavidEGrayson 4:d3b60bd43811 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 nop
DavidEGrayson 0:06475317f283 135
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 0:06475317f283 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 4:d3b60bd43811 151 nop
DavidEGrayson 0:06475317f283 152
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 0:06475317f283 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 4:d3b60bd43811 168 nop
DavidEGrayson 0:06475317f283 169
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 nop
DavidEGrayson 0:06475317f283 186
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 0:06475317f283 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 nop
DavidEGrayson 4:d3b60bd43811 203
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 0:06475317f283 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 4:d3b60bd43811 219 nop
DavidEGrayson 5:690fdfb595de 220 delay_region_end
DavidEGrayson 4:d3b60bd43811 221 bx lr ; return
DavidEGrayson 0:06475317f283 222
DavidEGrayson 0:06475317f283 223 END