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@10:f1bb84b97788, 2013-03-01 (annotated)

Committer:
DavidEGrayson
Date:
Fri Mar 01 04:15:35 2013 +0000
Revision:
10:f1bb84b97788
Parent:
9:6ffb85d69eaf
Child:
11:e00ba70ac54c
Saved one cycle per bit by shifting the delays to the left in C.

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 9:6ffb85d69eaf 29 push {r4, r5, r6, r7}
DavidEGrayson 9:6ffb85d69eaf 30 mov r4, lr
DavidEGrayson 9:6ffb85d69eaf 31 push {r4}
DavidEGrayson 10:f1bb84b97788 32
DavidEGrayson 9:6ffb85d69eaf 33 ldrb r4, [r0, #0] ; Load red.
DavidEGrayson 9:6ffb85d69eaf 34 lsls r4, r4, #24
DavidEGrayson 9:6ffb85d69eaf 35 mov r6, r4 ; Put red in MSB of r6.
DavidEGrayson 9:6ffb85d69eaf 36 ldrb r4, [r0, #1] ; Load green.
DavidEGrayson 9:6ffb85d69eaf 37 lsls r4, r4, #16
DavidEGrayson 10:f1bb84b97788 38 orrs r6, r6, r4 ; Put green in r6.
DavidEGrayson 9:6ffb85d69eaf 39 ldrb r4, [r0, #2] ; Load blue.
DavidEGrayson 9:6ffb85d69eaf 40 lsls r4, r4, #8
DavidEGrayson 10:f1bb84b97788 41 orrs r6, r6, r4 ; Put blue in MSB of r6.
DavidEGrayson 9:6ffb85d69eaf 42
DavidEGrayson 9:6ffb85d69eaf 43 ; On the Cortex M0 we simply did:
DavidEGrayson 9:6ffb85d69eaf 44 ; ldr r6, [r0] ; Read the color. Now we have: xxBbGgRr
DavidEGrayson 9:6ffb85d69eaf 45 ; rbit r6, r6 ; Reverse the order of the bits: rRgGbBxx
DavidEGrayson 9:6ffb85d69eaf 46 ; rev r6, r6 ; Reverse the order of the bytes: xxbBgGrR
DavidEGrayson 9:6ffb85d69eaf 47 ; and then we used rrxs for shifting to the right through carry.
DavidEGrayson 9:6ffb85d69eaf 48
DavidEGrayson 9:6ffb85d69eaf 49 ldr r7, =24 ; Initialize the loop counter register.
DavidEGrayson 0:06475317f283 50
DavidEGrayson 0:06475317f283 51 send_led_strip_bit
DavidEGrayson 0:06475317f283 52 str r3, [r1] ; Drive the line high.
DavidEGrayson 0:06475317f283 53
DavidEGrayson 7:9a088f042ee0 54 delay #0
DavidEGrayson 0:06475317f283 55
DavidEGrayson 9:6ffb85d69eaf 56 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 57 tst r6, r4
DavidEGrayson 9:6ffb85d69eaf 58 bne delay1
DavidEGrayson 9:6ffb85d69eaf 59 str r3, [r2] ; If the bit to send it 0, drive the line low.
DavidEGrayson 9:6ffb85d69eaf 60 delay1
DavidEGrayson 0:06475317f283 61
DavidEGrayson 7:9a088f042ee0 62 delay #1
DavidEGrayson 0:06475317f283 63
DavidEGrayson 9:6ffb85d69eaf 64 ldr r4, =0x80000000
DavidEGrayson 9:6ffb85d69eaf 65 tst r6, r4
DavidEGrayson 9:6ffb85d69eaf 66 beq delay2
DavidEGrayson 9:6ffb85d69eaf 67 str r3, [r2] ; If the bit to send is 1, drive the line low.
DavidEGrayson 9:6ffb85d69eaf 68 delay2
DavidEGrayson 0:06475317f283 69
DavidEGrayson 7:9a088f042ee0 70 delay #2
DavidEGrayson 4:d3b60bd43811 71
DavidEGrayson 10:f1bb84b97788 72 lsls r6, r6, #1 ; Shift color bits.
DavidEGrayson 6:9d0530b7dae2 73 subs r7, r7, #1 ; Decrement the loop counter.
DavidEGrayson 5:690fdfb595de 74 bne send_led_strip_bit ; Send another bit if we have not reached zero.
DavidEGrayson 4:d3b60bd43811 75
DavidEGrayson 4:d3b60bd43811 76 led_strip_asm_end
DavidEGrayson 9:6ffb85d69eaf 77 pop {r4}
DavidEGrayson 9:6ffb85d69eaf 78 mov lr, r4
DavidEGrayson 9:6ffb85d69eaf 79 pop {r4, r5, r6, r7}
DavidEGrayson 4:d3b60bd43811 80 bx lr
DavidEGrayson 4:d3b60bd43811 81
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