first commit

2025-03-06 11:15:32 +01:00
commit 7b30d6e298
5276 changed files with 2108927 additions and 0 deletions
--- a/libraries/GxEPD2/examples/GxEPD2_SerialFlash_Loader/GxEPD2_SerialFlash_Loader.ino
+++ b/libraries/GxEPD2/examples/GxEPD2_SerialFlash_Loader/GxEPD2_SerialFlash_Loader.ino
@@ -0,0 +1,459 @@
+// GxEPD2_SerialFlash_Loader : Display Library example for SPI e-paper panels from Dalian Good Display and boards from Waveshare.
+//
+// Display Library based on Demo Example from Good Display: https://www.good-display.com/companyfile/32/
+//
+// Author: Jean-Marc Zingg
+//
+// Version: see library.properties
+//
+// Library: https://github.com/ZinggJM/GxEPD2
+//
+// this example uses the SerialFlash library from: https://github.com/PaulStoffregen/SerialFlash
+// with a modification for use with ESP32 or the STM32 package available here: https://github.com/ZinggJM/SerialFlash
+// download it as .zip file and install with Library Mananger method "Add .ZIP Library..."
+//
+// this example can run on ESP6266 or ESP32 using WiFi connection
+
+// Supporting Arduino Forum Topics (closed, read only):
+// Good Display ePaper for Arduino: https://forum.arduino.cc/t/good-display-epaper-for-arduino/419657
+// Waveshare e-paper displays with SPI: https://forum.arduino.cc/t/waveshare-e-paper-displays-with-spi/467865
+//
+// Add new topics in https://forum.arduino.cc/c/using-arduino/displays/23 for new questions and issues
+
+#include <SerialFlash.h>
+
+// digital pin for flash chip CS pin:
+//const int FlashChipSelect = SS; // for standard slave select pin
+//const int FlashChipSelect = 5; // use D1 on my Wemos D1 mini wired for e-papers
+const int FlashChipSelect = 2; // as used with my ESP32 protoboard SD connector
+
+#if defined (ESP8266)
+#include <ESP8266WiFi.h>
+#endif
+
+#include <WiFiClient.h>
+#include <WiFiClientSecure.h>
+
+const char* ssid     = "........";
+const char* password = "........";
+const int httpPort  = 80;
+const int httpsPort = 443;
+const char* fp_api_github_com = "df b2 29 c6 a6 38 1a 59 9d c9 ad 92 2d 26 f5 3c 83 8f a5 87"; // as of 25.11.2020
+const char* fp_github_com     = "5f 3f 7a c2 56 9f 50 a4 66 76 47 c6 a1 8c a0 07 aa ed bb 8e"; // as of 25.11.2020
+const char* fp_rawcontent     = "70 94 de dd e6 c4 69 48 3a 92 70 a1 48 56 78 2d 18 64 e0 b7"; // as of 25.11.2020
+
+// note: the certificates have been moved to a separate header file, as R"CERT( destroys IDE Auto Format capability
+
+#include "GxEPD2_github_raw_certs.h"
+
+const char* certificate_rawcontent = cert_DigiCert_TLS_RSA_SHA256_2020_CA1; // ok, should work until 2031-04-13 23:59:59
+
+const char* host_rawcontent   = "raw.githubusercontent.com";
+const char* path_rawcontent   = "/ZinggJM/GxEPD2/master/extras/bitmaps/";
+const char* path_prenticedavid   = "/prenticedavid/MCUFRIEND_kbv/master/extras/bitmaps/";
+const char* path_waveshare_c  = "/waveshare/e-Paper/master/RaspberryPi_JetsonNano/c/pic/";
+const char* path_waveshare_py = "/waveshare/e-Paper/master/RaspberryPi_JetsonNano/python/pic/";
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println();
+  Serial.println("GxEPD2_SerialFlash_Loader");
+
+#ifdef RE_INIT_NEEDED
+  WiFi.persistent(true);
+  WiFi.mode(WIFI_STA); // switch off AP
+  WiFi.setAutoConnect(true);
+  WiFi.setAutoReconnect(true);
+  WiFi.disconnect();
+#endif
+
+  if (!WiFi.getAutoConnect() || ( WiFi.getMode() != WIFI_STA) || ((WiFi.SSID() != ssid) && String(ssid) != "........"))
+  {
+    Serial.println();
+    Serial.print("WiFi.getAutoConnect()=");
+    Serial.println(WiFi.getAutoConnect());
+    Serial.print("WiFi.SSID()=");
+    Serial.println(WiFi.SSID());
+    WiFi.mode(WIFI_STA); // switch off AP
+    Serial.print("Connecting to ");
+    Serial.println(ssid);
+    WiFi.begin(ssid, password);
+  }
+  int ConnectTimeout = 30; // 15 seconds
+  while (WiFi.status() != WL_CONNECTED)
+  {
+    delay(500);
+    Serial.print(".");
+    Serial.print(WiFi.status());
+    if (--ConnectTimeout <= 0)
+    {
+      Serial.println();
+      Serial.println("WiFi connect timeout");
+      return;
+    }
+  }
+  Serial.println();
+  Serial.println("WiFi connected");
+
+  // Print the IP address
+  Serial.println(WiFi.localIP());
+
+  setClock();
+
+  if (!SerialFlash.begin(FlashChipSelect)) 
+  {
+    Serial.println("Unable to access SPI Flash chip");
+    return;
+  }
+  Serial.println("SerialFlash started");
+  eraseSerialFlash();
+  listFiles();
+  downloadBitmaps_200x200();
+  downloadBitmaps_other();
+  downloadBitmaps_test();
+  listFiles();
+}
+
+void loop()
+{
+}
+
+void listFiles()
+{
+  Serial.println("All Files on SPI Flash chip:");
+  SerialFlash.opendir();
+  while (1) 
+  {
+    char filename[64];
+    uint32_t filesize;
+
+    if (SerialFlash.readdir(filename, sizeof(filename), filesize)) 
+    {
+      Serial.print("  ");
+      Serial.print(filename);
+      spaces(20 - strlen(filename));
+      Serial.print("  ");
+      Serial.print(filesize);
+      Serial.print(" bytes");
+      Serial.println();
+    } 
+    else 
+    {
+      Serial.println("no more files...");
+      break; // no more files
+    }
+  }
+}
+
+void spaces(int num) 
+{
+  for (int i=0; i < num; i++) 
+  {
+    Serial.print(" ");
+  }
+}
+
+void downloadFile_HTTPS(const char* host, const char* path, const char* filename, const char* fingerprint, const char* target, const char* certificate = certificate_rawcontent);
+
+void downloadBitmaps_200x200()
+{
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "logo200x200.bmp", fp_rawcontent, "logo200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "first200x200.bmp", fp_rawcontent, "first200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "second200x200.bmp", fp_rawcontent, "second200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "third200x200.bmp", fp_rawcontent, "third200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "fourth200x200.bmp", fp_rawcontent, "fourth200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "fifth200x200.bmp", fp_rawcontent, "fifth200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "sixth200x200.bmp", fp_rawcontent, "sixth200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "seventh200x200.bmp", fp_rawcontent, "seventh200x200.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "eighth200x200.bmp", fp_rawcontent, "eighth200x200.bmp");
+}
+
+void downloadBitmaps_other()
+{
+  downloadFile_HTTP("www.squix.org", "/blog/wunderground/", "chanceflurries.bmp", "chanceflurries.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "betty_1.bmp", fp_rawcontent, "betty_1.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "betty_4.bmp", fp_rawcontent, "betty_4.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "marilyn_240x240x8.bmp", fp_rawcontent, "marilyn_240x240x8.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "miniwoof.bmp", fp_rawcontent, "miniwoof.bmp");
+  //downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "test.bmp", fp_rawcontent, "test.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "tiger.bmp", fp_rawcontent, "tiger.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "tiger_178x160x4.bmp", fp_rawcontent, "tiger_178x160x4.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "tiger_240x317x4.bmp", fp_rawcontent, "tiger_240x317x4.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "tiger_320x200x24.bmp", fp_rawcontent, "tiger_320x200x24.bmp");
+  //downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "tiger16T.bmp", fp_rawcontent, "tiger16T.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_prenticedavid, "woof.bmp", fp_rawcontent, "woof.bmp");
+}
+
+void downloadBitmaps_test()
+{
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "output5.bmp", fp_rawcontent, "output5.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "output6.bmp", fp_rawcontent, "output6.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "tractor_1.bmp", fp_rawcontent, "tractor_1.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "tractor_4.bmp", fp_rawcontent, "tractor_4.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "tractor_8.bmp", fp_rawcontent, "tractor_8.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "tractor_11.bmp", fp_rawcontent, "tractor_11.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "tractor_44.bmp", fp_rawcontent, "tractor_44.bmp");
+  downloadFile_HTTPS(host_rawcontent, path_rawcontent, "tractor_88.bmp", fp_rawcontent, "tractor_88.bmp");
+}
+
+void downloadFile_HTTP(const char* host, const char* path, const char* filename, const char* target)
+{
+  WiFiClient client;
+  Serial.print("connecting to ");
+  Serial.println(host);
+  if (!client.connect(host, httpPort))
+  {
+    Serial.println("connection failed");
+    return;
+  }
+  Serial.print("requesting URL: ");
+  Serial.println(String("http://") + host + path + filename);
+  client.print(String("GET ") + path + filename + " HTTP/1.1\r\n" +
+               "Host: " + host + "\r\n" +
+               "User-Agent: GxEPD2_SerialFlash_Loader\r\n" +
+               "Connection: close\r\n\r\n");
+  Serial.println("request sent");
+  bool ok = false;
+  int32_t content_length = 0;
+  while (client.connected() || client.available())
+  {
+    String line = client.readStringUntil('\n');
+    if (!ok)
+    {
+      ok = line.startsWith("HTTP/1.1 200 OK");
+      if (ok) Serial.println(line);
+      //if (!ok) Serial.println(line);
+    }
+    if (!ok) Serial.println(line);
+    //Serial.println(line);
+    if (line.startsWith("Content-Length: "))
+    {
+      content_length = line.substring(16, line.length()).toInt();
+      Serial.print("content_length is "); Serial.println(content_length);
+    }
+    if (line == "\r")
+    {
+      Serial.println("headers received");
+      break;
+    }
+  }
+  if (!ok) return;
+  uint8_t buffer[512];
+#if defined(ESP8266)
+  client.peekBytes(buffer, 2);
+  Serial.write(buffer[0]); Serial.write(buffer[1]); Serial.println();
+#endif
+  size_t total = 0;
+  //if (!SerialFlash.createErasable(target, content_length)) // would use much more space
+  if (!SerialFlash.create(target, content_length))
+  {
+    Serial.print(target); Serial.println(" create failed");
+    return;
+  }
+  SerialFlashFile file = SerialFlash.open(target);
+  if (!file)
+  {
+    Serial.print(target); Serial.println(" open failed");
+    return;
+  }
+  while (client.connected() || client.available())
+  {
+    size_t available = client.available();
+    size_t fetch = available <= sizeof(buffer) ? available : sizeof(buffer);
+    if (fetch > 0)
+    {
+      size_t got = client.read(buffer, fetch);
+      file.write(buffer, got);
+      total += got;
+    }
+    delay(1); // yield();
+  }
+  file.close();
+  Serial.print("done, "); Serial.print(total); Serial.println(" bytes transferred");
+}
+
+void downloadFile_HTTPS(const char* host, const char* path, const char* filename, const char* fingerprint, const char* target, const char* certificate)
+{
+  // Use WiFiClientSecure class to create TLS connection
+#if defined (ESP8266)
+  BearSSL::WiFiClientSecure client;
+  BearSSL::X509List cert(certificate ? certificate : certificate_rawcontent);
+#else
+  WiFiClientSecure client;
+#endif
+  Serial.println(); Serial.print("downloading file \""); Serial.print(filename);  Serial.println("\"");
+  Serial.print("connecting to "); Serial.println(host);
+#if defined (ESP8266)
+  if (certificate) client.setTrustAnchors(&cert);
+  else if (fingerprint) client.setFingerprint(fingerprint);
+  else client.setInsecure();
+#elif defined (ESP32)
+  if (certificate) client.setCACert(certificate);
+#endif
+  if (!client.connect(host, httpsPort))
+  {
+    Serial.println("connection failed");
+    return;
+  }
+  Serial.print("requesting URL: ");
+  Serial.println(String("https://") + host + path + filename);
+  client.print(String("GET ") + path + filename + " HTTP/1.1\r\n" +
+               "Host: " + host + "\r\n" +
+               "User-Agent: GxEPD2_SerialFlash_Loader\r\n" +
+               "Connection: close\r\n\r\n");
+  Serial.println("request sent");
+  bool ok = false;
+  int32_t content_length = 0;
+  while (client.connected() || client.available())
+  {
+    String line = client.readStringUntil('\n');
+    if (!ok)
+    {
+      ok = line.startsWith("HTTP/1.1 200 OK");
+      if (ok) Serial.println(line);
+      //if (!ok) Serial.println(line);
+    }
+    if (!ok) Serial.println(line);
+    //Serial.print("line: "); Serial.println(line);
+    if (line.startsWith("Content-Length: "))
+    {
+      content_length = line.substring(16, line.length()).toInt();
+      Serial.print("content_length is "); Serial.println(content_length);
+    }
+    if (line == "\r")
+    {
+      Serial.println("headers received");
+      break;
+    }
+  }
+  if (!ok) return;
+  //return;
+  uint8_t buffer[512];
+#if defined(ESP8266)
+  client.peekBytes(buffer, 2);
+  Serial.write(buffer[0]); Serial.write(buffer[1]); Serial.println();
+#endif
+  size_t total = 0;
+  //if (!SerialFlash.createErasable(target, content_length)) // would use much more space
+  if (!SerialFlash.create(target, content_length))
+  {
+    Serial.print(target); Serial.println(" create failed");
+    return;
+  }
+  SerialFlashFile file = SerialFlash.open(target);
+  if (!file)
+  {
+    Serial.print(target); Serial.println(" open failed");
+    return;
+  }
+  while (client.connected() || client.available())
+  {
+    // this doesn't work as expected, but it helps for long downloads
+    int32_t start = millis();
+    for (int16_t t = 0, dly = 50; t < 20; t++, dly += 50)
+    {
+      if (!(client.connected() || client.available())) break;
+      if (client.available()) break; // read would not recover after having returned 0
+      delay(dly);
+    }
+    if (!(client.connected() || client.available())) break;
+    int32_t elapsed = millis() - start;
+    if (elapsed > 250)
+    {
+      Serial.print("waited for available "); Serial.print(millis() - start); Serial.print(" ms @ "); Serial.println(total);
+    }
+    size_t available = client.available();
+    if (0 == available)
+    {
+      Serial.print("download error: timeout on available() after "); Serial.print(total); Serial.println(" bytes");
+      break; // don't hang forever
+    }
+    size_t fetch = available <= sizeof(buffer) ? available : sizeof(buffer);
+    if (fetch > 0)
+    {
+      size_t got = client.read(buffer, fetch);
+      file.write(buffer, got);
+      total += got;
+    }
+    delay(1); // yield();
+    if (total > 30000) delay(250); // helps for long downloads
+  }
+  file.close();
+  Serial.print("done, "); Serial.print(total); Serial.println(" bytes transferred");
+}
+
+void eraseSerialFlash()
+{
+  unsigned char id[5];
+  SerialFlash.readID(id);
+  unsigned long size = SerialFlash.capacity(id);
+  unsigned long startMillis = millis();
+
+  if (size > 0) 
+  {
+    Serial.print("Flash Memory has ");
+    Serial.print(size);
+    Serial.println(" bytes.");
+    Serial.println("Erasing ALL Flash Memory:");
+    // Estimate the (lengthy) wait time.
+    Serial.print("  estimated wait: ");
+    int seconds = (float)size / eraseBytesPerSecond(id) + 0.5;
+    Serial.print(seconds);
+    Serial.println(" seconds.");
+    Serial.println("  Yes, full chip erase is SLOW!");
+    SerialFlash.eraseAll();
+    unsigned long dotMillis = millis();
+    unsigned char dotcount = 0;
+    while (SerialFlash.ready() == false) 
+    {
+      if (millis() - dotMillis > 1000) 
+      {
+        dotMillis = dotMillis + 1000;
+        Serial.print(".");
+        dotcount = dotcount + 1;
+        if (dotcount >= 60) 
+        {
+          Serial.println();
+          dotcount = 0;
+        }
+      }
+      yield();
+    }
+    if (dotcount > 0) Serial.println();
+    Serial.println("Erase completed");
+    unsigned long elapsed = millis() - startMillis;
+    Serial.print("  actual wait: ");
+    Serial.print(elapsed / 1000ul);
+    Serial.println(" seconds.");
+  }
+}
+
+float eraseBytesPerSecond(const unsigned char *id) 
+{
+  if (id[0] == 0x20) return 152000.0; // Micron
+  if (id[0] == 0x01) return 500000.0; // Spansion
+  if (id[0] == 0xEF) return 419430.0; // Winbond
+  if (id[0] == 0xC2) return 279620.0; // Macronix
+  return 320000.0; // guess?
+}
+
+// Set time via NTP, as required for x.509 validation
+void setClock()
+{
+  configTime(3 * 3600, 0, "pool.ntp.org", "time.nist.gov");
+
+  Serial.print("Waiting for NTP time sync: ");
+  time_t now = time(nullptr);
+  while (now < 8 * 3600 * 2)
+  {
+    delay(500);
+    Serial.print(".");
+    now = time(nullptr);
+  }
+  Serial.println("");
+  struct tm timeinfo;
+  gmtime_r(&now, &timeinfo);
+  Serial.print("Current time: ");
+  Serial.print(asctime(&timeinfo));
+}
--- a/libraries/GxEPD2/examples/GxEPD2_SerialFlash_Loader/GxEPD2_github_raw_certs.h
+++ b/libraries/GxEPD2/examples/GxEPD2_SerialFlash_Loader/GxEPD2_github_raw_certs.h
@@ -0,0 +1,142 @@
+// http://cacerts.digicert.com/DigiCertTLSRSASHA2562020CA1-1.crt
+// CN: DigiCert TLS RSA SHA256 2020 CA1 => name: DigiCert_TLS_RSA_SHA256_2020_CA1
+// not valid before: 2021-04-14 00:00:00
+// not valid after:  2031-04-13 23:59:59
+const char cert_DigiCert_TLS_RSA_SHA256_2020_CA1 [] PROGMEM = R"CERT(
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+  )CERT";
+
+// how to find the certificate was not easy. finally I found it using Mozilla Firefox.
+// opened one of the bitmaps, e.g. https://raw.githubusercontent.com/ZinggJM/GxEPD2/master/extras/bitmaps/logo200x200.bmp
+// clicked the lock symbol, Connection secure clicked >, show connection details, clicked More Information, clicked View Certificate, clicked Download PEM (chain),
+// Opened the .pem file and copied the pems into R"CERT(...)CERT"; strings.
+// for https://raw.githubusercontent.com all three pems work on ESP8266 and ESP32, if time is set from ntp.
+// but using a root certificate is preferred, as its validity may be longer.
+
+// https://raw.githubusercontent.com
+// issued by DigiCert Inc : DigiCert TLS RSA SHA256 2020 CA1
+// not valid before: Fri, 18 Mar 2022 00:00:00 GMT
+// not valid after:  Tue, 21 Mar 2023 23:59:59 GMT
+const char github_io_chain_pem_first [] PROGMEM = R"CERT(
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+)CERT";
+const char github_io_chain_pem_second [] PROGMEM = R"CERT(
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+)CERT";
+const char github_io_chain_pem_third [] PROGMEM = R"CERT(
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+)CERT";