Add libraries, picocalc notes.

libraries/TFT_eSPI/examples/GUI Widgets/Graphs/Graph_demo_1/Graph_demo_1.ino

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+// Demonstrate graph widget functions with a single trace instance
+// One trace can be drawn at a time with one trace instance
+
+// Requires widget library here:
+// https://github.com/Bodmer/TFT_eWidget
+
+#include <TFT_eSPI.h>
+TFT_eSPI tft = TFT_eSPI();
+
+#include <TFT_eWidget.h>               // Widget library
+
+GraphWidget gr = GraphWidget(&tft);    // Graph widget gr instance with pointer to tft
+TraceWidget tr = TraceWidget(&gr);     // Graph trace tr with pointer to gr
+
+const float gxLow  = 0.0;
+const float gxHigh = 100.0;
+const float gyLow  = -512.0;
+const float gyHigh = 512.0;
+
+void setup() {
+  Serial.begin(115200);
+
+  tft.begin();
+  tft.setRotation(3);
+  tft.fillScreen(TFT_BLACK);
+
+  // Graph area is 200 pixels wide, 150 pixels high, dark grey background
+  gr.createGraph(200, 150, tft.color565(5, 5, 5));
+
+  // x scale units is from 0 to 100, y scale units is -512 to 512
+  gr.setGraphScale(gxLow, gxHigh, gyLow, gyHigh);
+
+  // X grid starts at 0 with lines every 20 x-scale units
+  // Y grid starts at -512 with lines every 64 y-scale units
+  // blue grid
+  gr.setGraphGrid(gxLow, 20.0, gyLow, 64.0, TFT_BLUE);
+
+  // Draw empty graph, top left corner at pixel coordinate 40,10 on TFT
+  gr.drawGraph(40, 10);
+
+  // Start a trace with using red, trace points are in x and y scale units
+  // In this example a horizontal line is drawn
+  tr.startTrace(TFT_RED);
+  // Add a trace point at 0.0,0.0 on graph
+  tr.addPoint(0.0, 0.0);
+  // Add another point at 100.0, 0.0 this will be joined via line to the last point added
+  tr.addPoint(100.0, 0.0);
+
+  // Start a new trace with using white
+  tr.startTrace(TFT_WHITE);
+}
+
+void loop() {
+  static uint32_t plotTime = millis();
+  static float gx = 0.0, gy = 0.0;
+  static float delta = 10.0;
+
+  // Create a new plot point every 100ms
+  if (millis() - plotTime >= 100) {
+    plotTime = millis();
+
+    // Add a plot, first point in a trace will be a single pixel (if within graph area)
+    tr.addPoint(gx, gy);
+    gx += 1.0;
+    if (gy >  500.0) delta = -10.0;
+    if (gy < -500.0) delta =  10.0;
+    gy += delta;
+
+    // If the end of the graph x ais is reached start a new trace at 0.0,0.0
+    if (gx > gxHigh) {
+      gx = 0.0;
+      gy = 0.0;
+
+      // Draw empty graph at 40,10 on display to clear old one
+      gr.drawGraph(40, 10);
+      // Start new trace
+      tr.startTrace(TFT_GREEN);
+    }
+  }
+}