Merge pull request #4718 from thinkyhead/rc_twibus_patch_20160827

TWIBus patch for proper use of Wire.requestFrom

Marlin/twibus.cpp

@@ -25,7 +25,6 @@
 #if ENABLED(EXPERIMENTAL_I2CBUS)
 
 #include "twibus.h"
-
 #include <Wire.h>
 
 TWIBus::TWIBus() {
@@ -121,18 +120,12 @@ bool TWIBus::request(const uint8_t bytes) {
   #endif
 
   // requestFrom() is a blocking function
-  Wire.requestFrom(this->addr, bytes);
-
-  // Wait for all bytes to arrive
-  millis_t t = millis() + this->timeout;
-  while (Wire.available() < bytes)
-    if (ELAPSED(millis(), t)) {
-      #if ENABLED(DEBUG_TWIBUS)
-        SERIAL_ECHO_START;
-        SERIAL_ECHOLNPGM("i2c timeout");
-      #endif
-      return false;
-    }
+  if (Wire.requestFrom(this->addr, bytes) == 0) {
+    #if ENABLED(DEBUG_TWIBUS)
+      debug("request fail", this->addr);
+    #endif
+    return false;
+  }
 
   return true;
 }
@@ -151,6 +144,11 @@ uint8_t TWIBus::capture(char *dst, const uint8_t bytes) {
   uint8_t count = 0;
   while (count < bytes && Wire.available())
     dst[count++] = Wire.read();
+
+  #if ENABLED(DEBUG_TWIBUS)
+    debug(PSTR("capture"), count);
+  #endif
+
   return count;
 }
 

Marlin/twibus.h

@@ -54,14 +54,6 @@ typedef void (*twiRequestFunc_t)();
  */
 class TWIBus {
   private:
-    /**
-     * @brief Timeout value in milliseconds
-     * @details Maximum amount of time (ms) to wait for a reply.
-     *          Useful if something goes wrong on the bus and the
-     *          SDA/SCL lines are held up by another device.
-     */
-    const int timeout = 5;
-
     /**
      * @brief Number of bytes on buffer
      * @description Number of bytes in the buffer waiting to be flushed to the bus
@@ -165,11 +157,11 @@ class TWIBus {
     /**
      * @brief Request data from the slave device and wait.
      * @details Request a number of bytes from a slave device.
-     *          Wait for the data to arrive until the timeout
-     *          interval expires. Return true on success.
+     *          Wait for the data to arrive, and return true
+     *          on success.
      *
      * @param bytes the number of bytes to request
-     * @return status of the request: true=success, false=timeout
+     * @return status of the request: true=success, false=fail
      */
     bool request(const uint8_t bytes);