Init commit with many years of arduino sketches and projects. I dont know if the esp8266 includes much, but there are also libraries. I hope they dont have crazy automatic versioning through the Arduino IDE.

libraries/NewliquidCrystal/thirdparty libraries/SoftI2CMaster/examples/stretchTest/stretchTest.ino

@@ -0,0 +1,52 @@
+// This is a short sketch that stretches the low pulse on an I2C bus
+// in order to test the timeout feature.
+// Put any Arduino and I2C device, e.g. a memory chip, as usual on a breadboard,
+// then use another Arduino and flash this program into it. Connect the
+// pin 5 (of PORTD) with the SCL line and verify on the scope that the 
+// low period is indeed stretched.
+
+#include <avr/io.h>
+
+#define SCL_PORT PORTD
+#define SCL_PIN 5
+
+#define DELAY 8 // strech SCL low for that many milli seconds
+
+#define SCL_DDR       	(_SFR_IO_ADDR(SCL_PORT) - 1)
+#define SCL_OUT       	_SFR_IO_ADDR(SCL_PORT)
+#define SCL_IN		(_SFR_IO_ADDR(SCL_PORT) - 2)
+
+void initScl(void) {
+  asm volatile 
+  (" cbi      %[SCLDDR],%[SCLPIN]     ;release SCL \n\t" 
+   " cbi      %[SCLOUT],%[SCLPIN]     ;clear SCL output value \n\t" 
+   ::  [SCLDDR] "I"  (SCL_DDR), [SCLPIN] "I" (SCL_PIN), [SCLOUT] "I" (SCL_OUT));
+}
+
+void grabScl(void) {
+  asm volatile 
+    ("_L_wait: \n\t"
+     " sbic 	%[SCLIN],%[SCLPIN] \n\t"
+     " rjmp _L_wait \n\t"
+     "  sbi	%[SCLDDR],%[SCLPIN]"
+     ::[SCLDDR] "I"  (SCL_DDR), [SCLPIN] "I" (SCL_PIN), [SCLIN] "I" (SCL_IN));
+}
+
+void releaseScl(void) {
+  asm volatile
+    ("  cbi	%[SCLDDR],%[SCLPIN] \n\t"
+     :: [SCLDDR] "I"  (SCL_DDR), [SCLPIN] "I" (SCL_PIN));
+}
+
+void setup(void)
+{
+  Serial.begin(19200);
+  Serial.println("Intializing ...");
+  initScl();
+}
+
+void loop(void) {
+  grabScl();
+  delay(DELAY);
+  releaseScl();
+}