paul@50 | 1 | /* |
paul@50 | 2 | * Generate a VGA signal using a PIC32 microcontroller. |
paul@50 | 3 | * |
paul@50 | 4 | * Copyright (C) 2017, 2018 Paul Boddie <paul@boddie.org.uk> |
paul@50 | 5 | * |
paul@50 | 6 | * This program is free software: you can redistribute it and/or modify |
paul@50 | 7 | * it under the terms of the GNU General Public License as published by |
paul@50 | 8 | * the Free Software Foundation, either version 3 of the License, or |
paul@50 | 9 | * (at your option) any later version. |
paul@50 | 10 | * |
paul@50 | 11 | * This program is distributed in the hope that it will be useful, |
paul@50 | 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
paul@50 | 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
paul@50 | 14 | * GNU General Public License for more details. |
paul@50 | 15 | * |
paul@50 | 16 | * You should have received a copy of the GNU General Public License |
paul@50 | 17 | * along with this program. If not, see <http://www.gnu.org/licenses/>. |
paul@50 | 18 | */ |
paul@50 | 19 | |
paul@50 | 20 | #include "pic32_c.h" |
paul@53 | 21 | #include "init.h" |
paul@50 | 22 | #include "vga_display.h" |
paul@50 | 23 | |
paul@50 | 24 | |
paul@50 | 25 | |
paul@50 | 26 | /* Display state. */ |
paul@50 | 27 | |
paul@50 | 28 | vga_display_t vga_display; |
paul@50 | 29 | |
paul@56 | 30 | /* Pixel data. */ |
paul@56 | 31 | |
paul@56 | 32 | static const int ZERO_LENGTH = 1; |
paul@56 | 33 | static const uint8_t zerodata[1] = {0}; |
paul@56 | 34 | |
paul@50 | 35 | |
paul@50 | 36 | |
paul@50 | 37 | /* Initialise the state machine. */ |
paul@50 | 38 | |
paul@56 | 39 | void init_vga(display_config_t *display_config, int line_channels, |
paul@56 | 40 | int initiating_int_num) |
paul@50 | 41 | { |
paul@50 | 42 | /* Display parameters. */ |
paul@50 | 43 | |
paul@50 | 44 | vga_display.display_config = display_config; |
paul@56 | 45 | vga_display.line_channels = line_channels; |
paul@56 | 46 | vga_display.initiating_int_num = initiating_int_num; |
paul@50 | 47 | |
paul@50 | 48 | /* Initial state. */ |
paul@50 | 49 | |
paul@50 | 50 | vga_display.state_handler = vbp_active; |
paul@50 | 51 | vga_display.line = 0; |
paul@50 | 52 | } |
paul@50 | 53 | |
paul@56 | 54 | |
paul@56 | 55 | |
paul@56 | 56 | /* Configure DMA channels for the transfer of pixel data. */ |
paul@56 | 57 | |
paul@56 | 58 | void vga_configure_transfer(int transfer_int_num, uint32_t output) |
paul@56 | 59 | { |
paul@56 | 60 | int initiating_channel = vga_display.initiating_int_num >= 0; |
paul@56 | 61 | int dual_channel = vga_display.line_channels == 2; |
paul@56 | 62 | int channel = 0; |
paul@56 | 63 | |
paul@56 | 64 | /* Where dual line channels are involved, put the first before any |
paul@56 | 65 | initiating channel, chaining it to such a channel. */ |
paul@56 | 66 | |
paul@56 | 67 | if (dual_channel) |
paul@56 | 68 | { |
paul@56 | 69 | vga_configure_line_channel(channel++, transfer_int_num, |
paul@56 | 70 | initiating_channel ? dma_chain_next : dma_chain_none, |
paul@56 | 71 | output); |
paul@56 | 72 | } |
paul@56 | 73 | |
paul@56 | 74 | /* Introduce a special initiating channel if an interrupt has been |
paul@56 | 75 | indicated. */ |
paul@56 | 76 | |
paul@56 | 77 | if (initiating_channel) |
paul@56 | 78 | { |
paul@56 | 79 | vga_configure_zero_channel(channel++, vga_display.initiating_int_num, 1, |
paul@56 | 80 | output); |
paul@56 | 81 | } |
paul@56 | 82 | |
paul@56 | 83 | /* A line channel is always configured, chaining it to any initiating |
paul@56 | 84 | channel. */ |
paul@56 | 85 | |
paul@56 | 86 | vga_configure_line_channel(channel++, transfer_int_num, |
paul@56 | 87 | initiating_channel ? dma_chain_previous : dma_chain_none, |
paul@56 | 88 | output); |
paul@56 | 89 | |
paul@56 | 90 | /* A zero channel is always configured, chaining it to the preceding line |
paul@56 | 91 | channel, with the same transfer interrupt initiating the transfer. */ |
paul@56 | 92 | |
paul@56 | 93 | vga_configure_zero_channel(channel, transfer_int_num, 0, output); |
paul@56 | 94 | } |
paul@56 | 95 | |
paul@56 | 96 | void vga_configure_line_channel(int channel, int int_num, enum dma_chain chain, |
paul@56 | 97 | uint32_t output) |
paul@56 | 98 | { |
paul@56 | 99 | dma_init(channel, 2); |
paul@56 | 100 | |
paul@56 | 101 | /* If initiating, configure to always be enabled. */ |
paul@56 | 102 | |
paul@56 | 103 | if (chain == dma_chain_none) |
paul@56 | 104 | dma_set_auto_enable(channel, 1); |
paul@56 | 105 | |
paul@56 | 106 | /* Chain to either the previous or next channel where a special initiating |
paul@56 | 107 | channel is used. */ |
paul@56 | 108 | |
paul@56 | 109 | else |
paul@56 | 110 | dma_set_chaining(channel, chain); |
paul@56 | 111 | |
paul@56 | 112 | /* Initiate DMA on the transfer interrupt, transferring line data to the |
paul@56 | 113 | first byte of the output word. */ |
paul@56 | 114 | |
paul@56 | 115 | dma_set_interrupt(channel, int_num, 1); |
paul@56 | 116 | |
paul@56 | 117 | dma_set_destination(channel, HW_PHYSICAL(output), 1); |
paul@56 | 118 | dma_set_cell(channel, vga_display.display_config->transfer_cell_size); |
paul@56 | 119 | } |
paul@56 | 120 | |
paul@56 | 121 | void vga_configure_zero_channel(int channel, int int_num, int initiating, |
paul@56 | 122 | uint32_t output) |
paul@56 | 123 | { |
paul@56 | 124 | dma_init(channel, 3); |
paul@56 | 125 | |
paul@56 | 126 | /* If initiating, configure to always be enabled. */ |
paul@56 | 127 | |
paul@56 | 128 | if (initiating) |
paul@56 | 129 | dma_set_auto_enable(channel, 1); |
paul@56 | 130 | |
paul@56 | 131 | /* Otherwise, chain to the preceding channel and register prior transfer |
paul@56 | 132 | events before the channel is activated. */ |
paul@56 | 133 | |
paul@56 | 134 | else |
paul@56 | 135 | { |
paul@56 | 136 | dma_set_chaining(channel, dma_chain_previous); |
paul@56 | 137 | dma_set_receive_events(channel, 1); |
paul@56 | 138 | } |
paul@56 | 139 | |
paul@56 | 140 | /* Transfer upon the indicated interrupt condition. */ |
paul@56 | 141 | |
paul@56 | 142 | dma_set_interrupt(channel, int_num, 1); |
paul@56 | 143 | dma_set_transfer(channel, PHYSICAL((uint32_t) zerodata), |
paul@56 | 144 | ZERO_LENGTH, |
paul@56 | 145 | HW_PHYSICAL(output), 1, |
paul@56 | 146 | ZERO_LENGTH); |
paul@56 | 147 | } |
paul@56 | 148 | |
paul@53 | 149 | /* Configure a timer and output compare units for horizontal and vertical |
paul@53 | 150 | sync. */ |
paul@53 | 151 | |
paul@53 | 152 | void vga_configure_sync(int hsync_unit, int vsync_unit, int timer) |
paul@53 | 153 | { |
paul@54 | 154 | /* Record the peripherals in use. */ |
paul@54 | 155 | |
paul@54 | 156 | vga_display.hsync_unit = hsync_unit; |
paul@54 | 157 | vga_display.vsync_unit = vsync_unit; |
paul@54 | 158 | vga_display.timer = timer; |
paul@54 | 159 | |
paul@53 | 160 | /* Configure a timer for the horizontal sync. The timer has no prescaling |
paul@53 | 161 | (0). */ |
paul@53 | 162 | |
paul@53 | 163 | timer_init(timer, 0, vga_display.display_config->hfreq_limit); |
paul@53 | 164 | timer_on(timer); |
paul@53 | 165 | |
paul@53 | 166 | /* Horizontal sync. */ |
paul@53 | 167 | |
paul@53 | 168 | /* Configure output compare in dual compare (continuous output) mode using |
paul@53 | 169 | the timer as time base. The interrupt condition drives the first DMA |
paul@53 | 170 | channel and is handled to drive the display state machine. */ |
paul@53 | 171 | |
paul@53 | 172 | oc_init(hsync_unit, 0b101, timer); |
paul@53 | 173 | oc_set_pulse(hsync_unit, vga_display.display_config->hsync_end); |
paul@53 | 174 | oc_set_pulse_end(hsync_unit, vga_display.display_config->hsync_start); |
paul@53 | 175 | oc_init_interrupt(hsync_unit, 7, 3); |
paul@53 | 176 | oc_on(hsync_unit); |
paul@53 | 177 | |
paul@53 | 178 | /* Vertical sync. */ |
paul@53 | 179 | |
paul@53 | 180 | /* Configure output compare in single compare (output driven low) mode using |
paul@53 | 181 | the timer as time base. The unit is enabled later. It is only really used |
paul@53 | 182 | to achieve precisely-timed level transitions in hardware. */ |
paul@53 | 183 | |
paul@53 | 184 | oc_init(vsync_unit, 0b010, timer); |
paul@53 | 185 | oc_set_pulse(vsync_unit, 0); |
paul@53 | 186 | } |
paul@53 | 187 | |
paul@50 | 188 | |
paul@50 | 189 | |
paul@50 | 190 | /* Interrupt handlers. */ |
paul@50 | 191 | |
paul@50 | 192 | void vga_interrupt_handler(void) |
paul@50 | 193 | { |
paul@50 | 194 | vga_display.line += 1; |
paul@50 | 195 | vga_display.state_handler(); |
paul@50 | 196 | } |
paul@50 | 197 | |
paul@50 | 198 | |
paul@50 | 199 | |
paul@50 | 200 | /* Vertical back porch region. */ |
paul@50 | 201 | |
paul@50 | 202 | void vbp_active(void) |
paul@50 | 203 | { |
paul@50 | 204 | if (vga_display.line < vga_display.display_config->visible_start) |
paul@50 | 205 | return; |
paul@50 | 206 | |
paul@50 | 207 | /* Enter the visible region. */ |
paul@50 | 208 | |
paul@50 | 209 | vga_display.state_handler = visible_active; |
paul@50 | 210 | |
paul@50 | 211 | /* Set the line address. */ |
paul@50 | 212 | |
paul@50 | 213 | vga_display.linedata = vga_display.display_config->screen_start; |
paul@56 | 214 | start_visible(); |
paul@50 | 215 | } |
paul@50 | 216 | |
paul@50 | 217 | /* Visible region. */ |
paul@50 | 218 | |
paul@50 | 219 | void visible_active(void) |
paul@50 | 220 | { |
paul@50 | 221 | if (vga_display.line < vga_display.display_config->vfp_start) |
paul@50 | 222 | { |
paul@50 | 223 | /* Update the line address and handle wraparound. */ |
paul@50 | 224 | |
paul@50 | 225 | if (!(vga_display.line % vga_display.display_config->line_multiplier)) |
paul@50 | 226 | { |
paul@50 | 227 | vga_display.linedata += vga_display.display_config->line_length; |
paul@50 | 228 | |
paul@50 | 229 | if (vga_display.linedata >= vga_display.display_config->screen_limit) |
paul@50 | 230 | vga_display.linedata -= vga_display.display_config->screen_size; |
paul@50 | 231 | } |
paul@50 | 232 | |
paul@56 | 233 | update_visible(); |
paul@50 | 234 | return; |
paul@50 | 235 | } |
paul@50 | 236 | |
paul@50 | 237 | /* End the visible region. */ |
paul@50 | 238 | |
paul@50 | 239 | vga_display.state_handler = vfp_active; |
paul@50 | 240 | |
paul@50 | 241 | /* Disable the channel for the next line. */ |
paul@50 | 242 | |
paul@56 | 243 | stop_visible(); |
paul@50 | 244 | } |
paul@50 | 245 | |
paul@50 | 246 | /* Vertical front porch region. */ |
paul@50 | 247 | |
paul@50 | 248 | void vfp_active(void) |
paul@50 | 249 | { |
paul@50 | 250 | if (vga_display.line < vga_display.display_config->vsync_start) |
paul@50 | 251 | return; |
paul@50 | 252 | |
paul@50 | 253 | /* Enter the vertical sync region. */ |
paul@50 | 254 | |
paul@50 | 255 | vga_display.state_handler = vsync_active; |
paul@50 | 256 | |
paul@50 | 257 | /* Bring vsync low when the next line starts. */ |
paul@50 | 258 | |
paul@54 | 259 | vsync_low(); |
paul@50 | 260 | } |
paul@50 | 261 | |
paul@50 | 262 | /* Vertical sync region. */ |
paul@50 | 263 | |
paul@50 | 264 | void vsync_active(void) |
paul@50 | 265 | { |
paul@50 | 266 | if (vga_display.line < vga_display.display_config->vsync_end) |
paul@50 | 267 | return; |
paul@50 | 268 | |
paul@50 | 269 | /* Start again at the top of the display. */ |
paul@50 | 270 | |
paul@50 | 271 | vga_display.line = 0; |
paul@50 | 272 | vga_display.state_handler = vbp_active; |
paul@50 | 273 | |
paul@50 | 274 | /* Bring vsync high when the next line starts. */ |
paul@50 | 275 | |
paul@54 | 276 | vsync_high(); |
paul@50 | 277 | } |
paul@54 | 278 | |
paul@54 | 279 | |
paul@54 | 280 | |
paul@56 | 281 | /* Enable the channels for the next line. */ |
paul@56 | 282 | |
paul@56 | 283 | void start_visible(void) |
paul@56 | 284 | { |
paul@56 | 285 | update_visible(); |
paul@56 | 286 | update_transfers(1); |
paul@56 | 287 | } |
paul@56 | 288 | |
paul@56 | 289 | /* Update the channels for the next line. */ |
paul@56 | 290 | |
paul@56 | 291 | void update_visible(void) |
paul@56 | 292 | { |
paul@56 | 293 | uint32_t transfer_start = (uint32_t) vga_display.linedata; |
paul@56 | 294 | uint32_t transfer_length = vga_display.display_config->line_length / |
paul@56 | 295 | vga_display.line_channels; |
paul@56 | 296 | |
paul@56 | 297 | /* Determine whether an initiating channel is used. */ |
paul@56 | 298 | |
paul@56 | 299 | int initiating_channel = vga_display.initiating_int_num >= 0; |
paul@56 | 300 | int channel = 0; |
paul@56 | 301 | |
paul@56 | 302 | /* Update the source of a secondary line channel. */ |
paul@56 | 303 | |
paul@56 | 304 | if (vga_display.line_channels == 2) |
paul@56 | 305 | { |
paul@56 | 306 | dma_set_source(channel, PHYSICAL(transfer_start), transfer_length); |
paul@56 | 307 | transfer_start += transfer_length; |
paul@56 | 308 | channel++; |
paul@56 | 309 | } |
paul@56 | 310 | |
paul@56 | 311 | /* Skip any initiating channel. */ |
paul@56 | 312 | |
paul@56 | 313 | if (initiating_channel) |
paul@56 | 314 | channel++; |
paul@56 | 315 | |
paul@56 | 316 | /* Update the source of a line channel, with potentially updated start |
paul@56 | 317 | address. */ |
paul@56 | 318 | |
paul@56 | 319 | dma_set_source(channel, PHYSICAL(transfer_start), transfer_length); |
paul@56 | 320 | } |
paul@56 | 321 | |
paul@56 | 322 | /* Disable the channels for the next line. */ |
paul@56 | 323 | |
paul@56 | 324 | void stop_visible(void) |
paul@56 | 325 | { |
paul@56 | 326 | update_transfers(0); |
paul@56 | 327 | } |
paul@56 | 328 | |
paul@56 | 329 | /* Enable or disable transfers. */ |
paul@56 | 330 | |
paul@56 | 331 | void update_transfers(int enable) |
paul@56 | 332 | { |
paul@56 | 333 | int initiating_channel = vga_display.initiating_int_num >= 0; |
paul@56 | 334 | int channel = 0; |
paul@56 | 335 | void (*fn)() = enable ? dma_on : dma_off; |
paul@56 | 336 | |
paul@56 | 337 | /* Update line channels if no initiating channel is used. */ |
paul@56 | 338 | |
paul@56 | 339 | if (vga_display.line_channels == 2) |
paul@56 | 340 | { |
paul@56 | 341 | if (!initiating_channel) |
paul@56 | 342 | fn(channel); |
paul@56 | 343 | channel++; |
paul@56 | 344 | } |
paul@56 | 345 | |
paul@56 | 346 | /* Update any initiating channel. */ |
paul@56 | 347 | |
paul@56 | 348 | if (initiating_channel) |
paul@56 | 349 | { |
paul@56 | 350 | fn(channel); |
paul@56 | 351 | channel++; |
paul@56 | 352 | } |
paul@56 | 353 | |
paul@56 | 354 | /* Update line channels if no initiating channel is used. */ |
paul@56 | 355 | |
paul@56 | 356 | if (!initiating_channel) |
paul@56 | 357 | fn(channel); |
paul@56 | 358 | } |
paul@56 | 359 | |
paul@56 | 360 | |
paul@56 | 361 | |
paul@54 | 362 | /* Bring vsync low (single compare, output driven low) when the next line |
paul@54 | 363 | starts. */ |
paul@54 | 364 | |
paul@54 | 365 | void vsync_low(void) |
paul@54 | 366 | { |
paul@54 | 367 | oc_init(vga_display.vsync_unit, 0b010, vga_display.timer); |
paul@54 | 368 | oc_on(vga_display.vsync_unit); |
paul@54 | 369 | } |
paul@54 | 370 | |
paul@54 | 371 | /* Bring vsync high (single compare, output driven high) when the next line |
paul@54 | 372 | starts. */ |
paul@54 | 373 | |
paul@54 | 374 | void vsync_high(void) |
paul@54 | 375 | { |
paul@54 | 376 | oc_init(vga_display.vsync_unit, 0b001, vga_display.timer); |
paul@54 | 377 | oc_on(vga_display.vsync_unit); |
paul@54 | 378 | } |