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@12:b6df8ac053c8, 2013-03-01 (annotated)

Committer:
DavidEGrayson
Date:
Fri Mar 01 04:34:54 2013 +0000
Revision:
12:b6df8ac053c8
Parent:
11:e00ba70ac54c
Child:
19:46d7ab0ba3e7
Introduced the delay_fudges array.  The code still works for the M0.

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 7:9a088f042ee0 52 delay #0
DavidEGrayson 0:06475317f283 53
DavidEGrayson 9:6ffb85d69eaf 54 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 55 tst r6, r4
DavidEGrayson 9:6ffb85d69eaf 56 bne delay1
DavidEGrayson 12:b6df8ac053c8 57 str r3, [r2] ; If the bit to send it 0, drive the line low.
DavidEGrayson 9:6ffb85d69eaf 58 delay1
DavidEGrayson 0:06475317f283 59
DavidEGrayson 7:9a088f042ee0 60 delay #1
DavidEGrayson 0:06475317f283 61
DavidEGrayson 9:6ffb85d69eaf 62 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 63 tst r6, r4
DavidEGrayson 9:6ffb85d69eaf 64 beq delay2
DavidEGrayson 12:b6df8ac053c8 65 str r3, [r2] ; If the bit to send is 1, drive the line low.
DavidEGrayson 9:6ffb85d69eaf 66 delay2
DavidEGrayson 0:06475317f283 67
DavidEGrayson 7:9a088f042ee0 68 delay #2
DavidEGrayson 4:d3b60bd43811 69
DavidEGrayson 12:b6df8ac053c8 70 lsls r6, r6, #1 ; Shift color bits.
DavidEGrayson 6:9d0530b7dae2 71 subs r7, r7, #1 ; Decrement the loop counter.
DavidEGrayson 12:b6df8ac053c8 72 bne send_led_strip_bit ; Send another bit if we have not reached zero.
DavidEGrayson 12:b6df8ac053c8 73 pop {r4, r5, r6, r7, pc} ; Otherwise, restore the registers and return.
DavidEGrayson 4:d3b60bd43811 74
DavidEGrayson 4:d3b60bd43811 75
DavidEGrayson 4:d3b60bd43811 76 delay_region
DavidEGrayson 5:690fdfb595de 77 ; The following is 128 nops.
DavidEGrayson 0:06475317f283 78 nop
DavidEGrayson 0:06475317f283 79 nop
DavidEGrayson 0:06475317f283 80 nop
DavidEGrayson 0:06475317f283 81 nop
DavidEGrayson 0:06475317f283 82 nop
DavidEGrayson 0:06475317f283 83 nop
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 4:d3b60bd43811 91 nop
DavidEGrayson 4:d3b60bd43811 92 nop
DavidEGrayson 4:d3b60bd43811 93 nop
DavidEGrayson 4:d3b60bd43811 94
DavidEGrayson 0:06475317f283 95 nop
DavidEGrayson 0:06475317f283 96 nop
DavidEGrayson 0:06475317f283 97 nop
DavidEGrayson 0:06475317f283 98 nop
DavidEGrayson 0:06475317f283 99 nop
DavidEGrayson 0:06475317f283 100 nop
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 4:d3b60bd43811 111
DavidEGrayson 0:06475317f283 112 nop
DavidEGrayson 0:06475317f283 113 nop
DavidEGrayson 0:06475317f283 114 nop
DavidEGrayson 0:06475317f283 115 nop
DavidEGrayson 4:d3b60bd43811 116 nop
DavidEGrayson 4:d3b60bd43811 117 nop
DavidEGrayson 0:06475317f283 118 nop
DavidEGrayson 0:06475317f283 119 nop
DavidEGrayson 0:06475317f283 120 nop
DavidEGrayson 0:06475317f283 121 nop
DavidEGrayson 0:06475317f283 122 nop
DavidEGrayson 0:06475317f283 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
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 nop
DavidEGrayson 0:06475317f283 136 nop
DavidEGrayson 0:06475317f283 137 nop
DavidEGrayson 0:06475317f283 138 nop
DavidEGrayson 4:d3b60bd43811 139 nop
DavidEGrayson 4:d3b60bd43811 140 nop
DavidEGrayson 4:d3b60bd43811 141 nop
DavidEGrayson 4:d3b60bd43811 142 nop
DavidEGrayson 4:d3b60bd43811 143 nop
DavidEGrayson 4:d3b60bd43811 144 nop
DavidEGrayson 0:06475317f283 145
DavidEGrayson 0:06475317f283 146 nop
DavidEGrayson 0:06475317f283 147 nop
DavidEGrayson 0:06475317f283 148 nop
DavidEGrayson 0:06475317f283 149 nop
DavidEGrayson 0:06475317f283 150 nop
DavidEGrayson 0:06475317f283 151 nop
DavidEGrayson 0:06475317f283 152 nop
DavidEGrayson 0:06475317f283 153 nop
DavidEGrayson 0:06475317f283 154 nop
DavidEGrayson 0:06475317f283 155 nop
DavidEGrayson 4:d3b60bd43811 156 nop
DavidEGrayson 4:d3b60bd43811 157 nop
DavidEGrayson 4:d3b60bd43811 158 nop
DavidEGrayson 4:d3b60bd43811 159 nop
DavidEGrayson 4:d3b60bd43811 160 nop
DavidEGrayson 4:d3b60bd43811 161 nop
DavidEGrayson 0:06475317f283 162
DavidEGrayson 0:06475317f283 163 nop
DavidEGrayson 0:06475317f283 164 nop
DavidEGrayson 0:06475317f283 165 nop
DavidEGrayson 0:06475317f283 166 nop
DavidEGrayson 0:06475317f283 167 nop
DavidEGrayson 0:06475317f283 168 nop
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
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 nop
DavidEGrayson 0:06475317f283 187 nop
DavidEGrayson 0:06475317f283 188 nop
DavidEGrayson 0:06475317f283 189 nop
DavidEGrayson 4:d3b60bd43811 190 nop
DavidEGrayson 4:d3b60bd43811 191 nop
DavidEGrayson 4:d3b60bd43811 192 nop
DavidEGrayson 4:d3b60bd43811 193 nop
DavidEGrayson 4:d3b60bd43811 194 nop
DavidEGrayson 4:d3b60bd43811 195 nop
DavidEGrayson 4:d3b60bd43811 196
DavidEGrayson 0:06475317f283 197 nop
DavidEGrayson 0:06475317f283 198 nop
DavidEGrayson 0:06475317f283 199 nop
DavidEGrayson 0:06475317f283 200 nop
DavidEGrayson 0:06475317f283 201 nop
DavidEGrayson 0:06475317f283 202 nop
DavidEGrayson 4:d3b60bd43811 203 nop
DavidEGrayson 4:d3b60bd43811 204 nop
DavidEGrayson 4:d3b60bd43811 205 nop
DavidEGrayson 4:d3b60bd43811 206 nop
DavidEGrayson 4:d3b60bd43811 207 nop
DavidEGrayson 4:d3b60bd43811 208 nop
DavidEGrayson 4:d3b60bd43811 209 nop
DavidEGrayson 4:d3b60bd43811 210 nop
DavidEGrayson 4:d3b60bd43811 211 nop
DavidEGrayson 4:d3b60bd43811 212 nop
DavidEGrayson 5:690fdfb595de 213 delay_region_end
DavidEGrayson 4:d3b60bd43811 214 bx lr ; return
DavidEGrayson 0:06475317f283 215
DavidEGrayson 0:06475317f283 216 END