Make software I2C bitrate and waveform more accurate

Move default I2C bitrate to 100kbit/sec
espruino · May 17, 2018 · 3739ee5 · 3739ee5
1 parent 972584b
commit 3739ee5
Show file tree

Hide file tree

Showing 4 changed files with 10 additions and 4 deletions.
diff --git a/ChangeLog b/ChangeLog
@@ -18,6 +18,8 @@
             ESP32: Fix accidental initialisation of UART3 when switching to Telnet (fix #1362)
             nRF52: Added `NRF.setAddress` to allow the MAC address to be changed
             Added Graphics.setFontAlign for font alignment and rotation
+            Make software I2C bitrate and waveform more accurate
+            Move default I2C bitrate to 100kbit/sec
 
      1v97 : nRF52: fix NRF.on('connect',...) issue
             STM32: Fix setDeviceClockCmd error for USB.setConsole()

diff --git a/src/jshardware_common.c b/src/jshardware_common.c
@@ -39,6 +39,6 @@ void jshSPIInitInfo(JshSPIInfo *inf) {
 void jshI2CInitInfo(JshI2CInfo *inf) {
   inf->pinSCL = PIN_UNDEFINED;
   inf->pinSDA = PIN_UNDEFINED;
-  inf->bitrate = 50000; // Is what we used - shouldn't it be 100k?
+  inf->bitrate = 100000;
   inf->started = false;
 }
diff --git a/src/jsi2c.c b/src/jsi2c.c
@@ -45,8 +45,7 @@ bool jsi2cPopulateI2CInfo(
 const int I2C_TIMEOUT = 100000;
 
 static void dly(i2cInfo *inf) {
-  volatile int i;
-  for (i=inf->delay;i>0;i--);
+  if (inf->delay) jshDelayMicroseconds(inf->delay);
 }
 
 static void err(const char *s) {
@@ -92,6 +91,7 @@ static void i2c_wr_bit(i2cInfo *inf, bool b) {
   dly(inf);
   jshPinSetValue(inf->pinSCL, 1); // stop forcing SCL
   dly(inf);
+  dly(inf);
   int timeout = I2C_TIMEOUT;
   while (!jshPinGetValue(inf->pinSCL) && --timeout); // clock stretch
   if (!timeout) err("Timeout (wr)");
@@ -103,6 +103,7 @@ static bool i2c_rd_bit(i2cInfo *inf) {
   jshPinSetValue(inf->pinSDA, 1); // stop forcing SDA
   dly(inf);
   jshPinSetValue(inf->pinSCL, 1); // stop forcing SCL
+  dly(inf);
   int timeout = I2C_TIMEOUT;
   while (!jshPinGetValue(inf->pinSCL) && --timeout); // clock stretch
   if (!timeout) err("Timeout (rd)");
@@ -138,7 +139,8 @@ static void i2c_initstruct(i2cInfo *inf, JshI2CInfo *i) {
   inf->pinSDA = i->pinSDA;
   inf->pinSCL = i->pinSCL;
   inf->started = i->started;
-  inf->delay = 4000000/i->bitrate;
+  inf->delay = 250000/i->bitrate;
+  if (inf->delay<2) inf->delay=0;
 }
 
 // ----------------------------------------------------------------------------

diff --git a/src/jswrap_spi_i2c.c b/src/jswrap_spi_i2c.c
@@ -91,6 +91,8 @@ May return undefined if no device can be found.
   ]
 }
 Set up this SPI port as an SPI Master.
+
+**Note:** When using Software SPI, the baud rate will be ignored - data is sent as fast as possible.
  */
 void jswrap_spi_setup(
     JsVar *parent, //!< The variable that is the class instance of this function.