Add HTTP Server Example

Runs an HTTP server that will draw images on the screen. Useful for
setting up a small digital frame that can be remotely controlled.
Has a friendly Python client.

examples/http-server/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.5)
+
+set(EXTRA_COMPONENT_DIRS "../../")
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(http-server)

examples/http-server/README.md

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+# HTTP server
+
+Runs an HTTP server that will draw images on the screen.  
+Useful for setting up a small digital frame that can be remotely controlled.  
+
+## Config
+1. In `main/server.h`, edit `WIFI_SSID` and `WIFI_PASSWORD` to match your wifi config
+2. In `main/main.c`, edit `n_epd_setup` to refer to the right EPD screen
+
+## Running
+flash (`idf.py flash`), then connect the EPDiy to a power source (computer is fine).  
+The endpoints are:
+1. `GET /`, prints the screen temp / height / width as headers
+2. `POST /clear`, clears the screen
+3. `POST /draw`, expects:
+   1. a body that is a binary stream already encoded to EPDiy's standards (like the one in `dragon.h`).
+   2. Headers `width`, `height`
+   3. Optional headers `x`,`y` (default to 0)
+   4. Optional header `clear`, if set to nonzero integer will force-clear the screen before drawing
+
+## Helper script
+`send_image.py` is a friendlier client.
+```bash
+$ ./send_image.py ESP_IP info
+EpdInfo(width=1024, height=768, temperature=20)
+
+$ ./send_image.py ESP_IP clear
+# Clears the screen
+
+$ ./send_image.y ESP_IP draw /tmp/spooder-man.png
+# Draws on screen
+```
+Thanks to argparse, all arguments are visible with `--help`.  
+Requires `requests` and `PIL` (or Pillow)

examples/http-server/component.mk

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+#
+# "main" pseudo-component makefile.
+#
+# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)

examples/http-server/main/CMakeLists.txt

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+set(        
+    app_sources "epd.c" "server.c" "main.c"
+)
+
+idf_component_register(
+        SRCS ${app_sources} 
+        REQUIRES epdiy esp_wifi nvs_flash esp_http_server esp_netif
+)

examples/http-server/main/epd.c

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+#include "epd.h"
+
+static EpdiyHighlevelState hl;
+static EpdData data;
+
+static inline void checkError(enum EpdDrawError err) {
+    if (err != EPD_DRAW_SUCCESS) {
+        ESP_LOGE("demo", "draw error: %X", err);
+    }
+}
+
+EpdData n_epd_data() {
+    return data;
+}
+
+void n_epd_setup(const EpdDisplay_t* display) {
+    epd_init(&epd_board_v7, display, EPD_LUT_64K);
+    epd_set_vcom(1560);
+    hl = epd_hl_init(EPD_BUILTIN_WAVEFORM);
+    epd_set_rotation(EPD_ROT_LANDSCAPE);
+    data.width = epd_rotated_display_width();
+    data.height = epd_rotated_display_height();
+    data.temperature = epd_ambient_temperature();
+}
+
+void n_epd_clear() {
+    epd_poweron();
+    epd_fullclear(&hl, data.temperature);
+    epd_poweroff();
+}
+
+void n_epd_draw(uint8_t* content, int x, int y, int width, int height) {
+    uint8_t* fb = epd_hl_get_framebuffer(&hl);
+    EpdRect area = {
+        .x = x,
+        .y = y,
+        .width = width,
+        .height = height,
+    };
+    epd_draw_rotated_image(area, content, fb);
+    epd_poweron();
+    checkError(epd_hl_update_screen(&hl, MODE_GC16, data.temperature));
+    epd_poweroff();
+}

examples/http-server/main/epd.h

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+#ifndef EPD_H
+#define EPD_H
+
+#include "epdiy.h"
+#include <esp_log.h>
+
+typedef struct {
+    int width;
+    int height;
+    int temperature;
+} EpdData;
+
+EpdData n_epd_data();
+void n_epd_setup();
+void n_epd_clear();
+void n_epd_draw(uint8_t* content, int x, int y, int width, int height);
+#endif /* EPD_H */

examples/http-server/main/main.c

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+#include "server.h"
+#include "esp_http_server.h"
+#include "epd.h"
+#include "esp_heap_caps.h"
+#include "settings.h"
+
+#define WRITE_HEADER(req, buffer, name, format, src) \
+    sprintf(buffer, format, src);                    \
+    ESP_ERROR_CHECK(httpd_resp_set_hdr(req, name, buffer));
+static esp_err_t http_index(httpd_req_t* req) {
+    EpdData data = n_epd_data();
+    char width[20], height[20], temperature[20];
+    WRITE_HEADER(req, width, "width", "%d", data.width);
+    WRITE_HEADER(req, height, "height", "%d", data.height);
+    WRITE_HEADER(req, temperature, "temperature", "%d", data.temperature);
+    const char* response = "Hello! Check headers\n";
+    httpd_resp_set_type(req, "text/plain");
+    httpd_resp_set_status(req, "200");
+    httpd_resp_send(req, response, HTTPD_RESP_USE_STRLEN);
+    return ESP_OK;
+}
+
+esp_err_t http_clear(httpd_req_t* req) {
+    ESP_LOGI(__FUNCTION__, "Clear\n");
+    n_epd_clear();
+    const char* response = "Cleared\n";
+    httpd_resp_set_type(req, "text/plain");
+    httpd_resp_set_status(req, "200");
+    httpd_resp_send(req, response, HTTPD_RESP_USE_STRLEN);
+    return ESP_OK;
+}
+
+esp_err_t http_draw(httpd_req_t* req) {
+    // optional headers: x,y. Default to 0
+    // required headers: height, width
+    // Content should be a stream of special bytes - we're reading 4 bits at a time.
+    int x, y, width, height, clear;
+    char header[20];
+    memset(header, 0, 20);
+    if (httpd_req_get_hdr_value_str(req, "clear", header, 20) == ESP_OK) {
+        sscanf(header, "%d", &clear);
+    } else {
+        clear = 0;
+    }
+    if (httpd_req_get_hdr_value_str(req, "x", header, 20) == ESP_OK) {
+        sscanf(header, "%d", &x);
+    } else {
+        x = 0;
+    }
+    if (httpd_req_get_hdr_value_str(req, "y", header, 20) == ESP_OK) {
+        sscanf(header, "%d", &y);
+    } else {
+        y = 0;
+    }
+    if (httpd_req_get_hdr_value_str(req, "width", header, 20) == ESP_OK) {
+        sscanf(header, "%d", &width);
+    } else {
+        char response[60];
+        sprintf(response, "Missing header width");
+        httpd_resp_set_type(req, "text/plain");
+        httpd_resp_set_status(req, "400");
+        httpd_resp_send(req, response, HTTPD_RESP_USE_STRLEN);
+        return ESP_OK;
+    }
+    if (httpd_req_get_hdr_value_str(req, "height", header, 20) == ESP_OK) {
+        sscanf(header, "%d", &height);
+    } else {
+        char response[60];
+        sprintf(response, "Missing header height");
+        httpd_resp_set_type(req, "text/plain");
+        httpd_resp_set_status(req, "400");
+        httpd_resp_send(req, response, HTTPD_RESP_USE_STRLEN);
+        return ESP_OK;
+    }
+
+    // READING STREAM
+    int req_size = req->content_len;
+    char* content = (char*)heap_caps_malloc(req_size, MALLOC_CAP_SPIRAM);
+    if (content == NULL) {
+        char msg[50];
+        sprintf(msg, "Failed to allocate %d chars\n", req_size);
+        httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, msg);
+        return ESP_ERR_INVALID_ARG;
+    }
+    int current_pos = 0;
+    int amount_recieved;
+    while ((amount_recieved = httpd_req_recv(req, (content + current_pos), req_size)) > 0) {
+        ESP_LOGI(__FUNCTION__, "Read %d bytes\n", amount_recieved);
+        current_pos += amount_recieved;
+    }
+    if (amount_recieved < 0) {
+        char msg[50];
+        heap_caps_free(content);
+        ESP_LOGE(msg, "Failed to read byets. Error code %d\n", amount_recieved);
+        httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, msg);
+        return ESP_ERR_INVALID_ARG;
+    }
+    ESP_LOGI(__FUNCTION__, "Done reading %d bytes out of %d\n", current_pos, req_size);
+
+    if (clear) {
+        n_epd_clear();
+    }
+    n_epd_draw(((uint8_t*)content), x, y, width, height);
+    heap_caps_free(content);
+
+    // Done reading
+    char response[100];
+    sprintf(
+        response, "x %d, y %d, width %d, height %d, byte count %d\n", x, y, width, height, req_size
+    );
+    httpd_resp_set_type(req, "text/plain");
+    httpd_resp_set_status(req, "200");
+    httpd_resp_send(req, response, HTTPD_RESP_USE_STRLEN);
+    return ESP_OK;
+}
+
+void register_paths(httpd_handle_t server) {
+    {
+        httpd_uri_t uri
+            = { .uri = "/", .method = HTTP_GET, .handler = http_index, .user_ctx = NULL };
+        httpd_register_uri_handler(server, &uri);
+    }
+    {
+        httpd_uri_t uri
+            = { .uri = "/clear", .method = HTTP_POST, .handler = http_clear, .user_ctx = NULL };
+        httpd_register_uri_handler(server, &uri);
+    }
+    {
+        httpd_uri_t uri
+            = { .uri = "/draw", .method = HTTP_POST, .handler = http_draw, .user_ctx = NULL };
+        httpd_register_uri_handler(server, &uri);
+    }
+}
+
+void app_main(void) {
+    // Initialize NVS, needed for wifi
+    esp_err_t ret = nvs_flash_init();
+    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
+        ESP_ERROR_CHECK(nvs_flash_erase());
+        ret = nvs_flash_init();
+    }
+    ESP_ERROR_CHECK(ret);
+
+    httpd_handle_t server = get_server();
+    if (server != NULL) {
+        register_paths(server);
+    }
+    n_epd_setup(&SCREEN_MODEL);
+}

examples/http-server/main/server.c

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+#include "server.h"
+
+httpd_handle_t get_server(void);
+
+static void wifi_init_sta(void) {
+    // Initialize the ESP-NETIF
+    esp_netif_init();
+    esp_event_loop_create_default();
+
+    // Create default event loop
+    esp_netif_create_default_wifi_sta();
+
+    // Initialize the Wi-Fi driver
+    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
+    ESP_ERROR_CHECK(esp_wifi_init(&cfg));
+
+    // Set Wi-Fi mode to station
+    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
+
+    // Configure Wi-Fi connection
+    wifi_config_t wifi_config = {
+        .sta = {
+            .ssid = WIFI_SSID,
+            .password = WIFI_PASSWORD,
+        },
+    };
+
+    // Set the Wi-Fi configuration
+    ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_config));
+    ESP_ERROR_CHECK(esp_wifi_start());
+    ESP_ERROR_CHECK(esp_wifi_connect());
+}
+
+httpd_handle_t start_webserver(void) {
+    httpd_config_t config = HTTPD_DEFAULT_CONFIG();
+    config.lru_purge_enable = true;
+
+    httpd_handle_t server = NULL;
+    ESP_ERROR_CHECK(httpd_start(&server, &config));
+    return server;
+}
+
+httpd_handle_t get_server(void) {
+    wifi_init_sta();
+    return start_webserver();
+}

examples/http-server/main/server.h

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+#ifndef SERVER_H
+#define SERVER_H
+
+#include <stdio.h>
+#include <string.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "esp_event.h"
+#include "esp_log.h"
+#include "nvs_flash.h"
+#include "esp_wifi.h"
+#include "esp_netif.h"
+#include "esp_http_server.h"
+
+#include "settings.h"
+
+httpd_handle_t get_server(void);
+
+#endif /* SERVER_H */

examples/http-server/main/settings.h

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+#ifndef SETTINGS_H
+#define SETTINGS_H
+
+#define WIFI_SSID "best ssid"                    // Replace with your Wi-Fi SSID
+#define WIFI_PASSWORD "great password much wow"  // Replace with your Wi-Fi password
+
+#define SCREEN_MODEL ED060XC3
+
+#endif /* SETTINGS_H */