Added helper method to set motor current by RMS.

The code is copied from the TMCStepper project. The MIT licenses are compatible and a source mention has been made in code. This helper method simplifies correctly configuring the current.

Author: pvginkel

src/TMC2209.h

@@ -86,10 +86,16 @@ class TMC2209
   void setAllCurrentValues(uint8_t run_current_percent,
     uint8_t hold_current_percent,
     uint8_t hold_delay_percent);
+  void setRMSCurrent(uint16_t mA,
+    float rSense,
+    float holdMultiplier = 0.5f);
 
   void enableDoubleEdge();
   void disableDoubleEdge();
 
+  void enableVSense();
+  void disableVSense();
+
   void enableInverseMotorDirection();
   void disableInverseMotorDirection();
 
@@ -279,6 +285,9 @@ class TMC2209
   const static uint8_t STEPPER_DRIVER_FEATURE_OFF = 0;
   const static uint8_t STEPPER_DRIVER_FEATURE_ON = 1;
 
+  const static int MAX_READ_RETRIES = 5;
+  const static uint32_t READ_RETRY_DELAY_MS = 20;
+
   // Datagrams
   const static uint8_t WRITE_READ_REPLY_DATAGRAM_SIZE = 8;
   const static uint8_t DATA_SIZE = 4;
@@ -504,6 +513,8 @@ class TMC2209
   const static uint8_t MRES_001 = 0b1000;
   const static uint8_t DOUBLE_EDGE_DISABLE = 0;
   const static uint8_t DOUBLE_EDGE_ENABLE = 1;
+  const static uint8_t VSENSE_DISABLE = 0;
+  const static uint8_t VSENSE_ENABLE = 1;
 
   const static size_t MICROSTEPS_PER_STEP_MIN = 1;
   const static size_t MICROSTEPS_PER_STEP_MAX = 256;

src/TMC2209/TMC2209.cpp

@@ -223,6 +223,30 @@ void TMC2209::setAllCurrentValues(uint8_t run_current_percent,
   writeStoredDriverCurrent();
 }
 
+void TMC2209::setRMSCurrent(uint16_t mA,
+  float rSense,
+  float holdMultiplier)
+{
+  // Taken from https://github.com/teemuatlut/TMCStepper/blob/74e8e6881adc9241c2e626071e7328d7652f361a/src/source/TMCStepper.cpp#L41.
+
+  uint8_t CS = 32.0*1.41421*mA/1000.0*(rSense+0.02)/0.325 - 1;
+  // If Current Scale is too low, turn on high sensitivity R_sense and calculate again
+  if (CS < 16) {
+    enableVSense();
+    CS = 32.0*1.41421*mA/1000.0*(rSense+0.02)/0.180 - 1;
+  } else { // If CS >= 16, turn off high_sense_r
+    disableVSense();
+  }
+
+  if (CS > 31) {
+    CS = 31;
+  }
+
+  driver_current_.irun = CS;
+  driver_current_.ihold = CS*holdMultiplier;
+  writeStoredDriverCurrent();
+}
+
 void TMC2209::enableDoubleEdge()
 {
   chopper_config_.double_edge = DOUBLE_EDGE_ENABLE;
@@ -235,6 +259,18 @@ void TMC2209::disableDoubleEdge()
   writeStoredChopperConfig();
 }
 
+void TMC2209::enableVSense()
+{
+  chopper_config_.vsense = VSENSE_ENABLE;
+  writeStoredChopperConfig();
+}
+
+void TMC2209::disableVSense()
+{
+  chopper_config_.vsense = VSENSE_DISABLE;
+  writeStoredChopperConfig();
+}
+
 void TMC2209::enableInverseMotorDirection()
 {
   global_config_.shaft = 1;