Add support for ssd1315 displays

This PR adds supporf for ssd1315 displays. ssd1315 is mostly compatible with ssd1306 drivers, but it has some small differences, such as requiring a special initialization sequence and needing an explicit column address reset when updating.

It also includes a small optimization in do_update, that fixed this error i was getting:
`E (1225) SSD1306: I2C write failed for display update: 0x107` [(a timeout)](https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/error-codes.html)

The initialization sequence is based on the one used in [u8g2](https://github.com/olikraus/u8g2/blob/dbd338af5d57b219e48ea1ffdb97c4153668676c/csrc/u8x8_d_ssd1315_128x64_noname.c).

Tested on an ESP32.

Author: clsource

display_driver.c

@@ -67,6 +67,8 @@ Context *display_create_port(GlobalContext *global, term opts)
         ctx = ili948x_display_create_port(global, opts);
     } else if (!strcmp(compat_string, "solomon-systech,ssd1306")) {
         ctx = ssd1306_display_create_port(global, opts);
+    } else if (!strcmp(compat_string, "solomon-systech,ssd1315")) {
+        ctx = ssd1306_display_create_port(global, opts);
     } else if (!strcmp(compat_string, "sino-wealth,sh1106")) {
         ctx = ssd1306_display_create_port(global, opts);
     } else if (!strcmp(compat_string, "sitronix,st7789")

ssd1306_display_driver.c

@@ -42,6 +42,7 @@
 #define CHAR_WIDTH 8
 
 #define I2C_ADDRESS 0x3C
+#define I2C_CHUNK_SIZE 64
 
 #define CTRL_BYTE_CMD_SINGLE 0x80
 #define CTRL_BYTE_CMD_STREAM 0x00
@@ -53,11 +54,18 @@
 #define CMD_SET_COM_SCAN_MODE 0xC8
 #define CMD_SET_CHARGE_PUMP 0x8D
 
+typedef enum
+{
+    DISPLAY_SSD1306,
+    DISPLAY_SSD1315,
+    DISPLAY_SH1106,
+} display_type_t;
+
 // TODO: let's change name, since also non SPI display are supported now
 struct SPI
 {
     term i2c_host;
-    bool is_sh1106;
+    display_type_t type;
     Context *ctx;
 };
 
@@ -116,8 +124,9 @@ static void do_update(Context *ctx, term display_list)
 
             i2c_master_write_byte(cmd, CTRL_BYTE_CMD_SINGLE, true);
             i2c_master_write_byte(cmd, 0xB0 | ypos / 8, true);
-            if (spi->is_sh1106) {
-                // set the column, otherwise the starting column will be somewhere in the middle
+
+            if (spi->type == DISPLAY_SH1106 || spi->type == DISPLAY_SSD1315) {
+                // SSD1315 and SH1106 require explicit column address reset
                 i2c_master_write_byte(cmd, CTRL_BYTE_CMD_SINGLE, true);
                 i2c_master_write_byte(cmd, 0x00, true);
                 i2c_master_write_byte(cmd, CTRL_BYTE_CMD_SINGLE, true);
@@ -126,19 +135,26 @@ static void do_update(Context *ctx, term display_list)
             i2c_master_write_byte(cmd, CTRL_BYTE_DATA_STREAM, true);
 
 
-            if (spi->is_sh1106) {
+            if (spi->type == DISPLAY_SH1106) {
                 // add 2 empty pages on sh1106 since it can have up to 132 pixels
                 // and 128 pixel screen starts at (2, 0)
                 i2c_master_write_byte(cmd, 0, true);
                 i2c_master_write_byte(cmd, 0, true);
             }
 
-            for (uint8_t j = 0; j < DISPLAY_WIDTH; j++) {
-                i2c_master_write_byte(cmd, out_buf[j], true);
+            // send pages in chunks to avoid timeout error (0x107)
+            int offset = 0;
+            while (offset < DISPLAY_WIDTH) {
+                int chunk_len = DISPLAY_WIDTH - offset;
+                if (chunk_len > I2C_CHUNK_SIZE) {
+                    chunk_len = I2C_CHUNK_SIZE;
+                }
+                i2c_master_write(cmd, out_buf + offset, chunk_len, true);
+                offset += chunk_len;
             }
 
             // no need to send the last 2 page, the position will be set on next line again
-            // if (spi->is_sh1106) {
+            // if (spi->type == DISPLAY_SH1106) {
             //    i2c_master_write_byte(cmd, 0, true);
             //    i2c_master_write_byte(cmd, 0, true);
             // }
@@ -176,12 +192,17 @@ static void display_init(Context *ctx, term opts)
     ctx->platform_data = spi;
 
     spi->ctx = ctx;
+    spi->type = DISPLAY_SSD1306; // Default to SSD1306
 
     term compat_value_term = interop_kv_get_value_default(opts, ATOM_STR("\xA", "compatible"), term_nil(), ctx->global);
     int str_ok;
     char *compat_string = interop_term_to_string(compat_value_term, &str_ok);
     if (str_ok && compat_string) {
-        spi->is_sh1106 = !strcmp(compat_string, "sino-wealth,sh1106");
+        if (!strcmp(compat_string, "sino-wealth,sh1106")) {
+            spi->type = DISPLAY_SH1106;
+        } else if (!strcmp(compat_string, "solomon-systech,ssd1315")) {
+            spi->type = DISPLAY_SSD1315;
+        }
         free(compat_string);
     } else {
         return;
@@ -209,11 +230,60 @@ static void display_init(Context *ctx, term opts)
     i2c_master_write_byte(cmd, (I2C_ADDRESS << 1) | I2C_MASTER_WRITE, true);
     i2c_master_write_byte(cmd, CTRL_BYTE_CMD_STREAM, true);
 
-    i2c_master_write_byte(cmd, CMD_SET_CHARGE_PUMP, true);
-    i2c_master_write_byte(cmd, 0x14, true);
+    if (spi->type == DISPLAY_SSD1315) {
+        /*
+         * Init sequence derived from u8g2 project (BSD-2-Clause).
+         * Source: https://github.com/olikraus/u8g2
+         * 
+         * These values are standard hardware initialization commands
+         * defined by the Solomon Systech SSD1315 datasheet.
+         */
+
+        i2c_master_write_byte(cmd, 0xAE, true);  // Display OFF
+        
+        i2c_master_write_byte(cmd, 0xD5, true);  // Set Display Clock Divide Ratio / Oscillator Frequency
+        i2c_master_write_byte(cmd, 0x80, true);  // 0x80 is standard/stable
+        
+        i2c_master_write_byte(cmd, 0xA8, true);  // Set Multiplex Ratio
+        i2c_master_write_byte(cmd, 0x3F, true);  // 64 MUX
+        
+        i2c_master_write_byte(cmd, 0xD3, true);  // Set Display Offset
+        i2c_master_write_byte(cmd, 0x00, true);  // No offset
+        
+        i2c_master_write_byte(cmd, 0x40, true);  // Set Display Start Line to 0
+        
+        i2c_master_write_byte(cmd, 0x8D, true);  // Set Charge Pump
+        i2c_master_write_byte(cmd, 0x14, true);  // Enable Charge Pump
+        
+        i2c_master_write_byte(cmd, 0xA1, true);  // Set Segment Remap
+        i2c_master_write_byte(cmd, 0xC8, true);  // Set COM Scan Mode
+        
+        i2c_master_write_byte(cmd, 0xDA, true);  // Set COM Pins Hardware Configuration
+        i2c_master_write_byte(cmd, 0x12, true);  // Alternative COM pin config
+        
+        i2c_master_write_byte(cmd, 0x81, true);  // Set Contrast Control
+        i2c_master_write_byte(cmd, 0xCF, true);  // Use High Contrast (0xCF) as per u8x8
+        
+        i2c_master_write_byte(cmd, 0xD9, true);  // Set Pre-charge Period
+        i2c_master_write_byte(cmd, 0xF1, true);  // 0xF1 is required for stable 400kHz operation
+        
+        i2c_master_write_byte(cmd, 0xDB, true);  // Set VCOMH Deselect Level
+        i2c_master_write_byte(cmd, 0x40, true);  // 0x40 (approx 0.77x VCC)
+        
+        i2c_master_write_byte(cmd, 0xA4, true);  // Resume to RAM content display
+        i2c_master_write_byte(cmd, 0xA6, true);  // Normal Display (not inverted)
+        
+        i2c_master_write_byte(cmd, 0xAD, true);  // Internal IREF Setting
+        i2c_master_write_byte(cmd, 0x10, true);  // Internal Iref
+        
+        i2c_master_write_byte(cmd, 0xAF, true);  // Display ON
+    } else {
+        i2c_master_write_byte(cmd, CMD_SET_CHARGE_PUMP, true);
+        i2c_master_write_byte(cmd, 0x14, true);
 
-    i2c_master_write_byte(cmd, CMD_SET_SEGMENT_REMAP, true);
-    i2c_master_write_byte(cmd, CMD_SET_COM_SCAN_MODE, true);
+        i2c_master_write_byte(cmd, CMD_SET_SEGMENT_REMAP, true);
+        i2c_master_write_byte(cmd, CMD_SET_COM_SCAN_MODE, true);
+    }
 
     if (invert) {
         i2c_master_write_byte(cmd, CMD_DISPLAY_INVERTED, true);
@@ -224,7 +294,7 @@ static void display_init(Context *ctx, term opts)
 
     esp_err_t res = i2c_master_cmd_begin(i2c_num, cmd, 50 / portTICK_PERIOD_MS);
     if (res != ESP_OK) {
-        ESP_LOGE(TAG, "ssd1306 OLED configuration failed. error: 0x%.2X", res);
+        ESP_LOGE(TAG, "ssd1306/ssd1315 OLED configuration failed. error: 0x%.2X", res);
     } else {
         xTaskCreate(process_messages, "display", 10000, spi, 1, NULL);
     }