General • PIO won't generate 8-bit VGA signals

Code:

#include "pico/stdlib.h"#include "hardware/pio.h"#include "hardware/dma.h"#include "hsync.pio.h"#include "vsync.pio.h"#include "rgb.pio.h"#define TXCOUNT 307200 // Total pixelsuint8_t vga_data_array[TXCOUNT];uint8_t * address_pointer = &vga_data_array[0] ;#define HSYNC 07    #define VSYNC 06// VGA timing constants#define H_ACTIVE   655    // (active + frontporch - 1) - one cycle delay for mov#define V_ACTIVE   479    // (active - 1)#define RGB_ACTIVE 639    // (horizontal active) - 1// Screen width/height#define _width 640#define _height 480void setup() {  memset(vga_data_array, 0b11111111, TXCOUNT);  Serial.begin(115200);  PIO pio = pio0;  uint hsync_offset = pio_add_program(pio, &hsync_program);  uint vsync_offset = pio_add_program(pio, &vsync_program);  uint rgb_offset = pio_add_program(pio, &rgb_program);  // Manually select a few state machines from pio instance pio0.  uint hsync_sm = 0;  uint vsync_sm = 1;  uint rgb_sm = 2;  // Call the initialization functions that are defined within each PIO file.  // Why not create these programs here? By putting the initialization function in  // the pio file, then all information about how to use/setup that state machine  // is consolidated in one place. Here in the C, we then just import and use it.  hsync_program_init(pio, hsync_sm, hsync_offset, HSYNC);  vsync_program_init(pio, vsync_sm, vsync_offset, VSYNC);  rgb_program_init(pio, rgb_sm, rgb_offset, 8);  /////////////////////////////////////////////////////////////////////////////////////////////////////  // ============================== PIO DMA Channels =================================================  /////////////////////////////////////////////////////////////////////////////////////////////////////  // DMA channels - 0 sends color data, 1 reconfigures and restarts 0  int rgb_chan_0 = dma_claim_unused_channel(true);  int rgb_chan_1 = dma_claim_unused_channel(true);  // Channel Zero (sends color data to PIO VGA machine)  dma_channel_config c0 = dma_channel_get_default_config(rgb_chan_0);  // default configs  channel_config_set_transfer_data_size(&c0, DMA_SIZE_8);              // 8-bit txfers  channel_config_set_read_increment(&c0, true);                        // yes read incrementing  channel_config_set_write_increment(&c0, false);                      // no write incrementing  channel_config_set_dreq(&c0, DREQ_PIO0_TX2) ;                        // DREQ_PIO0_TX2 pacing (FIFO)  channel_config_set_chain_to(&c0, rgb_chan_1);                        // chain to other channel  dma_channel_configure(      rgb_chan_0,                 // Channel to be configured      &c0,                        // The configuration we just created      &pio->txf[rgb_sm],          // write address (RGB PIO TX FIFO)      &vga_data_array,            // The initial read address (pixel color array)      TXCOUNT,                    // Number of transfers; in this case each is 1 byte.      false                       // Don't start immediately.  );  // Channel One (reconfigures the first channel)  dma_channel_config c1 = dma_channel_get_default_config(rgb_chan_1);   // default configs  channel_config_set_transfer_data_size(&c1, DMA_SIZE_32);              // 32-bit txfers  channel_config_set_read_increment(&c1, false);                        // no read incrementing  channel_config_set_write_increment(&c1, false);                       // no write incrementing  channel_config_set_chain_to(&c1, rgb_chan_0);                         // chain to other channel  dma_channel_configure(      rgb_chan_1,                         // Channel to be configured      &c1,                                // The configuration we just created      &dma_hw->ch[rgb_chan_0].read_addr,  // Write address (channel 0 read address)      &address_pointer,                   // Read address (POINTER TO AN ADDRESS)      1,                                  // Number of transfers, in this case each is 4 byte      false                               // Don't start immediately.  );  /////////////////////////////////////////////////////////////////////////////////////////////////////  /////////////////////////////////////////////////////////////////////////////////////////////////////  // Initialize PIO state machine counters. This passes the information to the state machines  // that they retrieve in the first 'pull' instructions, before the .wrap_target directive  // in the assembly. Each uses these values to initialize some counting registers.  pio_sm_put_blocking(pio, hsync_sm, H_ACTIVE);  pio_sm_put_blocking(pio, vsync_sm, V_ACTIVE);  pio_sm_put_blocking(pio, rgb_sm, RGB_ACTIVE);  // Start the two pio machine IN SYNC  // Note that the RGB state machine is running at full speed,  // so synchronization doesn't matter for that one. But, we'll  // start them all simultaneously anyway.  pio_enable_sm_mask_in_sync(pio, ((1u << hsync_sm) | (1u << vsync_sm) | (1u << rgb_sm)));  // Start DMA channel 0. Once started, the contents of the pixel color array  // will be continously DMA's to the PIO machines that are driving the screen.  // To change the contents of the screen, we need only change the contents  // of that array.  dma_start_channel_mask((1u << rgb_chan_0)) ;}void loop() {  }

Code:

;; Hunter Adams (vha3@cornell.edu); RGB generation for VGA driver; mod by Bruce Land for 16 colors; Program name.program rgbpull block ; Pull from FIFO to OSR (only once)mov y, osr ; Copy value from OSR to y scratch register.wrap_targetset pins, 0 ; Zero RGB pins in blankingmov x, y ; Initialize counter variablewait 1 irq 1 [3]; Wait for vsync active mode (starts 5 cycles after execution)colorout:pull block; Pull color valueout pins, 8[2]; Push out to pins (first byte)jmp x-- colorout; Stay here thru horizontal active mode.wrap% c-sdk {static inline void rgb_program_init(PIO pio, uint sm, uint offset, uint pin) {    // creates state machine configuration object c, sets    // to default configurations. I believe this function is auto-generated    // and gets a name of <program name>_program_get_default_config    // Yes, page 40 of SDK guide    pio_sm_config c = rgb_program_get_default_config(offset);    // Map the state machine's SET and OUT pin group to three pins, the `pin`    // parameter to this function is the lowest one. These groups overlap.    sm_config_set_set_pins(&c, pin, 8);    sm_config_set_out_pins(&c, pin, 8);    // Set clock division (Commented out, this one runs at full speed)    // sm_config_set_clkdiv(&c, 5) ;    // Set this pin's GPIO function (connect PIO to the pad)    pio_gpio_init(pio, pin);    pio_gpio_init(pio, pin+1);    pio_gpio_init(pio, pin+2);    pio_gpio_init(pio, pin+3);    pio_gpio_init(pio, pin+4);    pio_gpio_init(pio, pin+5);    pio_gpio_init(pio, pin+6);    pio_gpio_init(pio, pin+7);        // Set the pin direction to output at the PIO (8 pins)    pio_sm_set_consecutive_pindirs(pio, sm, pin, 8, true);    // Load our configuration, and jump to the start of the program    pio_sm_init(pio, sm, offset, &c);    // Set the state machine running (commented out, I'll start this in the C)    // pio_sm_set_enabled(pio, sm, true);}%}

Code:

// -------------------------------------------------- //// This file is autogenerated by pioasm; do not edit! //// -------------------------------------------------- //#pragma once#if !PICO_NO_HARDWARE#include "hardware/pio.h"#endif// ----- //// hsync //// ----- //#define hsync_wrap_target 1#define hsync_wrap 8static const uint16_t hsync_program_instructions[] = {    0x80a0, //  0: pull   block                                  //     .wrap_target    0xa027, //  1: mov    x, osr                         0x0042, //  2: jmp    x--, 2                         0xff00, //  3: set    pins, 0                [31]    0xff00, //  4: set    pins, 0                [31]    0xff00, //  5: set    pins, 0                [31]    0xff01, //  6: set    pins, 1                [31]    0xec01, //  7: set    pins, 1                [12]    0xc100, //  8: irq    nowait 0               [1]             //     .wrap};#if !PICO_NO_HARDWAREstatic const struct pio_program hsync_program = {    .instructions = hsync_program_instructions,    .length = 9,    .origin = -1,};static inline pio_sm_config hsync_program_get_default_config(uint offset) {    pio_sm_config c = pio_get_default_sm_config();    sm_config_set_wrap(&c, offset + hsync_wrap_target, offset + hsync_wrap);    return c;}static inline void hsync_program_init(PIO pio, uint sm, uint offset, uint pin) {    // creates state machine configuration object c, sets    // to default configurations. I believe this function is auto-generated    // and gets a name of <program name>_program_get_default_config    // Yes, page 40 of SDK guide    pio_sm_config c = hsync_program_get_default_config(offset);    // Map the state machine's SET pin group to one pin, namely the `pin`    // parameter to this function.    sm_config_set_set_pins(&c, pin, 1);    // Set clock division (div by 5.9583 for 25 MHz state machine)    sm_config_set_clkdiv(&c, 5.9583) ;    // Set this pin's GPIO function (connect PIO to the pad)    pio_gpio_init(pio, pin);    // pio_gpio_init(pio, pin+1);    // Set the pin direction to output at the PIO    pio_sm_set_consecutive_pindirs(pio, sm, pin, 1, true);    // Load our configuration, and jump to the start of the program    pio_sm_init(pio, sm, offset, &c);    // Set the state machine running (commented out so can be synchronized w/ vsync)    // pio_sm_set_enabled(pio, sm, true);}#endif