Intermediary commit. Nothing's working, everything is broken. Let's start over now...

include/config.h

@@ -1,9 +1,32 @@
 #pragma once
 #include <Arduino.h>
 
-#define PIN_SD_CS            D1
-#define PIN_VS1053_CS        D2
-#define PIN_RC522_CS         D3
+// Pins according to https://www.instructables.com/id/NodeMCU-ESP8266-Details-and-Pinout/
+// D0 = 16
+// D1 = 5
+// D2 = 4
+// D3 = 0
+// D4 = 2
+// D5 = 14
+// D6 = 12
+// D7 = 13
+// D8 = 15
+// A0 = 17
+// Other usable pins:
+// 6, 7, 8, 11 not readable
+// 1, 3, 6, 7, 8, 11 nor writable -> 1 (TX) and 3 (RX) can be used read-only
+// 9 -> S2
+// 10 -> S3
+#define RX 3
+#define TX 1
+
+
+#define PIN_SD_CS            D4
+#define PIN_VS1053_XCS        D8
+#define PIN_VS1053_XRESET    D3
+#define PIN_VS1053_XDCS    D1
+#define PIN_VS1053_DREQ    D2
+#define PIN_RC522_CS         D0
 
 #define PIN_BTN_VOL_UP       D4
 #define PIN_BTN_VOL_DOWN     D5

include/controller.h

@@ -1,13 +1,15 @@
 #pragma once
 
 #include "player.h"
+#include "sd_card.h"
 
 class Controller {
 private:
 	Player* _player;
+	SDCard* _sd_card;
 
 public:
-	Controller(Player* p) : _player(p) {}
+	Controller(Player* p, SDCard* c) : _player(p), _sd_card(c) {}
 	void vol_up();
 	void vol_down();
 	void track_next();

include/player.h

@@ -1,7 +1,27 @@
 #pragma once
+#include "sd_card.h"
+#include "config.h"
+
+#define SCI_MODE 0x00
+#define SCI_STATUS 0x01
+#define SCI_CLOCKF 0x03
+
+#define CMD_WRITE 0x02
+#define CMD_READ 0x03
+
+#define XRESET PIN_VS1053_XRESET
+#define DREQ PIN_VS1053_DREQ
 
 class Player {
+private:
+	SDCard* _sd_card;
+	void _reset();
+	void _init();
+	void _wait();
+	uint16_t _read_register(uint8_t address, uint32_t spi_speed, uint16_t t);//=SPI_CLOCK_DIV4);
+	void _write_register(uint8_t address, uint16_t value, uint32_t spi_speed);//=SPI_CLOCK_DIV2);
 public:
+	Player(SDCard* c);
 	void vol_up();
 	void vol_down();
 	void track_next();

include/sd_card.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <SD.h>
+#include "config.h"
+
+class SDCard {
+public:
+	SDCard();
+};

include/spi_master.h

@@ -0,0 +1,27 @@
+#pragma once
+
+class SPIMaster {
+public:
+	static void init() {
+		SPI.setHwCs(false);
+		pinMode(PIN_SD_CS, OUTPUT);
+		pinMode(PIN_VS1053_XCS, OUTPUT);
+		pinMode(PIN_VS1053_XDCS, OUTPUT);
+	}
+	static void enable(uint8_t pin) {
+		digitalWrite(PIN_SD_CS, pin==PIN_SD_CS ? LOW : HIGH);
+		digitalWrite(PIN_VS1053_XCS, pin==PIN_VS1053_XCS ? LOW : HIGH);
+		digitalWrite(PIN_VS1053_XDCS, pin==PIN_VS1053_XDCS ? LOW : HIGH);
+	}
+
+	static void printStatus() {
+		Serial.printf("CS state: SD:%d, VS1053_XCS:%d, VS1053_XDCS:%d\n",
+			digitalRead(PIN_SD_CS),
+			digitalRead(PIN_VS1053_XCS),
+			digitalRead(PIN_VS1053_XDCS));
+	}
+
+	static void disable() {
+		enable(142);
+	}
+};

platformio.ini

@@ -12,3 +12,5 @@
 platform = espressif8266
 board = esp12e
 framework = arduino
+upload_port = /dev/cu.wchusbserial1420
+upload_speed = 921600

src/main.cpp

@@ -1,16 +1,52 @@
 #include <Arduino.h>
+#include <SPI.h>
 #include "config.h"
 #include "buttons.h"
 #include "controller.h"
 #include "player.h"
+#include "sd_card.h"
+#include "spi_master.h"
 
 Buttons* buttons;
 Controller* controller;
 Player* player;
+SDCard* sd;
+
+void printDirectory(File dir, int numTabs) {
+  while (true) {
+
+    File entry =  dir.openNextFile();
+    if (! entry) {
+      // no more files
+      break;
+    }
+    for (uint8_t i = 0; i < numTabs; i++) {
+      Serial.print('\t');
+    }
+    Serial.print(entry.name());
+    if (entry.isDirectory()) {
+      Serial.println("/");
+      printDirectory(entry, numTabs + 1);
+    } else {
+      // files have sizes, directories do not
+      Serial.print("\t\t");
+      Serial.println(entry.size(), DEC);
+    }
+    entry.close();
+  }
+}
 
 void setup() {
-	player = new Player();
-	controller = new Controller(player);
+	Serial.begin(74880);
+	Serial.println("Starting.");
+
+	Serial.println("Setting up SPI...");
+	SPI.begin();
+	SPIMaster::init();
+
+	sd = new SDCard();
+	player = new Player(sd);
+	controller = new Controller(player, sd);
 	buttons = new Buttons(controller);
 }
 

src/player.cpp

@@ -0,0 +1,99 @@
+// Based on https://github.com/mpflaga/Arduino_Library-vs1053_for_SdFat/blob/master/src/vs1053_SdFat.cpp
+
+#include "player.h"
+#include "spi_master.h"
+
+Player::Player(SDCard* c) {
+	pinMode(XRESET, OUTPUT);
+	digitalWrite(XRESET, HIGH);
+	pinMode(DREQ, INPUT);
+
+	_init();
+}
+
+void Player::_reset() {
+	digitalWrite(XRESET, LOW);
+	delay(50);
+	digitalWrite(XRESET, HIGH);
+	delay(50);
+}
+
+void Player::_init() {
+	SPI.setClockDivider(SPI_CLOCK_DIV16);
+
+	_reset();
+	uint16_t result;
+	for(uint8_t x=0; x<255; x++) {
+		result = _read_register(SCI_MODE, 0, x);
+		if (result != 0) Serial.printf("Try %3d: 0x%04X\n", x, result);
+	}
+	delay(10);
+	/*_read_register(SCI_MODE, SPI_CLOCK_DIV16); // First read fails for some unknown reason...
+	_read_register(SCI_MODE, SPI_CLOCK_DIV16);
+	_read_register(SCI_STATUS, SPI_CLOCK_DIV16);
+
+	_read_register(SCI_STATUS, SPI_CLOCK_DIV16);
+
+
+	_read_register(SCI_MODE, SPI_CLOCK_DIV16);
+	_read_register(SCI_MODE, SPI_CLOCK_DIV16);
+	uint16_t response = _read_register(SCI_MODE, SPI_CLOCK_DIV16);
+	if (response != 0x4800) {
+		Serial.printf("Initialization failed. SCI_MODE was: 0x%04X. Expected: 0x4800\n", response);
+		return;
+	}*/
+	/*_write_register(SCI_CLOCKF, 0x6000); // Set multiplier to 3x
+	delay(10);
+	response = _read_register(SCI_CLOCKF);
+	if (response != 0x6000) {
+		Serial.printf("Initialization failed. SCI_CLOCKF was: 0x%04X. Expected: 0x6000\n", response);
+		return;
+	}*/
+	//Serial.println(result, HEX);
+}
+
+inline void Player::_wait() {
+	delayMicroseconds(100);
+	//Serial.print("Waiting for DREQ...");
+	while(!digitalRead(DREQ));
+	//Serial.printf(" done (%d cycles).\n", i);
+}
+
+uint16_t Player::_read_register(uint8_t address, uint32_t spi_speed, uint16_t t) {
+	Serial.printf("Try %03d, querying register 0x%02X...", t, address);
+	//SPI.setClockDivider(spi_speed);
+	if (t & (1<<1)) _wait();
+	SPIMaster::enable(PIN_VS1053_XCS);
+	if (t & (1<<2)) _wait();
+	//_wait();
+	SPI.transfer(CMD_READ);
+	if (t & (1<<3)) _wait();
+	SPI.transfer(address);
+	if (t & (1<<4)) _wait();
+	uint8_t b1 = SPI.transfer(0xFF);
+	if (t & (1<<5)) _wait();
+	uint8_t b2 = SPI.transfer(0xFF);
+	if (t & (1<<6)) _wait();
+
+	uint16_t result = b1 << 8 | b2;
+	Serial.printf("Response: 0x%02X 0x%02X -> 0x%04X\n", b1, b2, result);
+	if (t & (1<<7)) delay(10);
+
+	//_wait();
+	//SPIMaster::disable();
+
+	return result;
+}
+
+void Player::_write_register(uint8_t address, uint16_t value, uint32_t spi_speed) {
+	Serial.printf("Writing to register 0x%02X...", address);
+	SPI.setClockDivider(spi_speed);
+	SPIMaster::enable(PIN_VS1053_XCS);
+	SPI.transfer(CMD_WRITE);
+	SPI.transfer(address);
+	SPI.transfer(value >> 8);
+	SPI.transfer(value & 0xFF);
+	_wait();
+	SPIMaster::disable();
+	Serial.println(" done.");
+}

src/sd_card.cpp

@@ -0,0 +1,9 @@
+#include "sd_card.h"
+
+SDCard::SDCard() {
+	if (!SD.begin(PIN_SD_CS)) {
+		Serial.println("Could not initialize SD card.");
+	} else {
+		Serial.println("SD card successfully initialized.");
+	}
+}