add ESP32C3

GPIO/ESP32/ring.ESP32C3.ino

+//
+// ring.ESP32C3.ino
+//    ESP32C3 ring oscillator test
+//    connect GPIO 8 and 20
+//
+// Neil Gershenfeld 12/26/22
+//
+// This work may be reproduced, modified, distributed,
+// performed, and displayed for any purpose, but must
+// acknowledge this project. Copyright is retained and
+// must be preserved. The work is provided as is; no
+// warranty is provided, and users accept all liability.
+//
+
+uint32_t input,output;
+
+void setup() {
+   pinMode(8,OUTPUT);
+   output = (1 << 8);
+   input = (1 << 20);
+   }
+
+void loop() {
+   //
+   // direct port I/O version
+   //    3.79 MHz at 160 MHz clock
+   //
+   /**/
+   while (1) {
+      if (GPIO.in.val & input)
+         GPIO.out_w1tc.val = output;
+      else
+         GPIO.out_w1ts.val = output;
+      }
+   /**/
+   //
+   // Arduino version
+   //    736 kHz at 166 MHz clock
+   //
+   /*
+   while (1) {
+      if (digitalRead(20))
+         digitalWrite(8,LOW);
+      else
+         digitalWrite(8,HIGH);
+      }
+   */
+   }