DigiPots support

Makefile

@@ -33,7 +33,7 @@ CLOCK      = 16000000L
 PROGRAMMER ?= -c avrisp2 -P usb
 SOURCE    = main.c motion_control.c gcode.c spindle_control.c coolant_control.c serial.c \
              protocol.c stepper.c eeprom.c settings.c planner.c nuts_bolts.c limits.c \
-             print.c probe.c report.c system.c sleep.c jog.c
+             print.c probe.c report.c system.c sleep.c jog.c current_control.c
 BUILDDIR = build
 SOURCEDIR = grbl
 # FUSES      = -U hfuse:w:0xd9:m -U lfuse:w:0x24:m

doc/csv/setting_codes_en_US.csv

@@ -33,3 +33,6 @@
 "130","X-axis maximum travel","millimeters","Maximum X-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances."
 "131","Y-axis maximum travel","millimeters","Maximum Y-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances."
 "132","Z-axis maximum travel","millimeters","Maximum Z-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances."
+"140","X-axis DigiPot value","integer","Value from 0-255 to send to the digital potentiometer. Determines the amount of current provided by the stepper motor."
+"141","Y-axis DigiPot value","integer","Value from 0-255 to send to the digital potentiometer. Determines the amount of current provided by the stepper motor."
+"142","Z-axis DigiPot value","integer","Value from 0-255 to send to the digital potentiometer. Determines the amount of current provided by the stepper motor."

doc/markdown/interface.md

@@ -314,6 +314,9 @@ ok
 | **`130`** | X-axis maximum travel, millimeters |
 | **`131`** | Y-axis maximum travel, millimeters |
 | **`132`** | Z-axis maximum travel, millimeters |
+| **`140`** | X-axis DigiPot setting, integer |
+| **`141`** | Y-axis DigiPot setting, integer |
+| **`142`** | Z-axis DigiPot setting, integer |
 
 
 - The other `$Nx=line` message is the print-out of a user-defined startup line, where `x` denotes the startup line order and ranges from `0` to `1` by default. The `line` denotes the startup line to be executed by Grbl upon reset or power-up, except during an ALARM.

doc/markdown/settings.md

@@ -257,3 +257,7 @@ Again, like the max rate setting, the simplest way to determine the values for t
 #### $130, $131, $132 – [X,Y,Z] Max travel, mm
 
 This sets the maximum travel from end to end for each axis in mm. This is only useful if you have soft limits (and homing) enabled, as this is only used by Grbl's soft limit feature to check if you have exceeded your machine limits with a motion command.
+
+#### $140, $141, $142 – [X,Y,Z] DigiPot setting, integer
+
+This is the value sent to the digital potentiometer (if present) to control how much current is provided by the stepper drivers.

grbl/config.h

@@ -622,6 +622,13 @@
 #define RPM_LINE_A4  1.203413e-01  // Used N_PIECES = 4. A and B constants of line 4.
 #define RPM_LINE_B4  1.151360e+03
 
+// When HAS_DIGIPOTS is defined in cpu_map.h, these values get sent over SPI during initialization
+// to configure the DigiPots, thus programatically setting the stepper current. This code
+// has been tested to work with AD5206 DigiPots but may work with other SPI-based DigiPots
+// as well.
+#define DEFAULT_X_CURRENT 135
+#define DEFAULT_Y_CURRENT 135
+#define DEFAULT_Z_CURRENT 135
 
 /* ---------------------------------------------------------------------------------------
    OEM Single File Configuration Option

grbl/cpu_map.h

@@ -130,6 +130,23 @@
   #define SPINDLE_PWM_PORT  PORTH
   #define SPINDLE_PWM_BIT		4 // MEGA2560 Digital Pin 7
 
+  // DigiPot pins
+  // #define HAS_DIGIPOTS
+  // DigiPot Slave Select (SS) pin configuration
+  #define DIGIPOTSS_DDR DDRD
+  #define DIGIPOTSS_PORT PORTD
+  #define DIGIPOTSS_BIT 7
+  #define SPI_DDR DDRB
+  #define SPI_PORT PORTB
+  #define MOSI_BIT 2
+  #define SCK_BIT 1
+  #define SS_BIT 0
+
+  // X Y Z digipot channels to stepper driver mapping
+  #define DIGIPOT_CHANNELS  { 4,5,3 }
+  #ifndef DIGIPOT_MOTOR_CURRENT
+    #define DIGIPOT_MOTOR_CURRENT { 135,135,135 }   // Values 0-255
+  #endif
 #endif
 
 #ifdef CPU_MAP_2560_RAMPS_BOARD // (Arduino Mega 2560) with Ramps 1.4 Board

grbl/current_control.c

@@ -0,0 +1,66 @@
+/*
+  current_control.c - methods for setting DigiPots over SPI
+  Part of Grbl
+
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
+
+  Grbl is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Grbl is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "current_control.h"
+#include "grbl.h"
+
+#ifdef HAS_DIGIPOTS
+
+void current_init()
+{
+    static const uint8_t digipot_motor_current[] = DIGIPOT_MOTOR_CURRENT;
+    // Set the SS pin to high
+    SPI_DDR |= (1<<SS_BIT);
+
+    // Set DIGIPOTSS_PIN as output
+    DIGIPOTSS_DDR |= 1<<DIGIPOTSS_BIT;
+    // Set MOSI, SCK as Output
+    SPI_DDR |= (1<<MOSI_BIT)|(1<<SCK_BIT);
+
+    // Initialize SPI as master
+    SPCR = (1<<SPE)|(1<<MSTR);
+
+    uint8_t i;
+    for (i = 0; i < N_AXIS; i++) {
+        set_current(i, digipot_motor_current[i]);
+    }
+}
+
+inline static uint8_t spi_transfer(uint8_t data)
+{
+    SPDR = data;
+    while (!(SPSR & (1<<SPIF))); // wait
+    return SPDR;
+}
+
+void set_current(uint8_t motor, uint8_t value)
+{
+    const uint8_t digipot_ch[] = DIGIPOT_CHANNELS;
+
+    // Take the SS pin low to select the chip
+    DIGIPOTSS_PORT &= ~(1<<DIGIPOTSS_BIT);
+    // Send the address and value via SPI
+    spi_transfer(digipot_ch[motor]);
+    spi_transfer(value);
+    // Take the SS pin high to de-select the chip
+    DIGIPOTSS_PORT |= (1<<DIGIPOTSS_BIT);
+}
+
+#endif // HAS_DIGIPOTS

grbl/current_control.h

@@ -0,0 +1,24 @@
+/*
+  current_control.h - methods for setting DigiPots over SPI
+  Part of Grbl
+
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
+
+  Grbl is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Grbl is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdint.h>
+
+void current_init();
+void set_current(uint8_t motor, uint8_t value);

grbl/grbl.h

@@ -41,10 +41,10 @@
 // Define the Grbl system include files. NOTE: Do not alter organization.
 #include "config.h"
 #include "nuts_bolts.h"
+#include "cpu_map.h"
 #include "settings.h"
 #include "system.h"
 #include "defaults.h"
-#include "cpu_map.h"
 #include "planner.h"
 #include "coolant_control.h"
 #include "eeprom.h"
@@ -61,6 +61,7 @@
 #include "stepper.h"
 #include "jog.h"
 #include "sleep.h"
+#include "current_control.h"
 
 // ---------------------------------------------------------------------------------------
 // COMPILE-TIME ERROR CHECKING OF DEFINE VALUES:

grbl/main.c

@@ -41,6 +41,9 @@ int main(void)
   // Initialize system upon power-up.
   serial_init();   // Setup serial baud rate and interrupts
   settings_init(); // Load Grbl settings from EEPROM
+#ifdef HAS_DIGIPOTS
+  current_init();  // Configure stepper driver current
+#endif // HAS_DIGIPOTS
   stepper_init();  // Configure stepper pins and interrupt timers
   system_init();   // Configure pinout pins and pin-change interrupt
 

grbl/report.c

@@ -214,6 +214,9 @@ void report_grbl_settings() {
         case 1: report_util_float_setting(val+idx,settings.max_rate[idx],N_DECIMAL_SETTINGVALUE); break;
         case 2: report_util_float_setting(val+idx,settings.acceleration[idx]/(60*60),N_DECIMAL_SETTINGVALUE); break;
         case 3: report_util_float_setting(val+idx,-settings.max_travel[idx],N_DECIMAL_SETTINGVALUE); break;
+        #ifdef HAS_DIGIPOTS
+        case 4: report_util_float_setting(val+idx,settings.current[idx],N_DECIMAL_SETTINGVALUE); break;
+        #endif // HAS_DIGIPOTS
       }
     }
     val += AXIS_SETTINGS_INCREMENT;

grbl/settings.c

@@ -57,7 +57,13 @@ const __flash settings_t defaults = {\
     .acceleration[Z_AXIS] = DEFAULT_Z_ACCELERATION,
     .max_travel[X_AXIS] = (-DEFAULT_X_MAX_TRAVEL),
     .max_travel[Y_AXIS] = (-DEFAULT_Y_MAX_TRAVEL),
-    .max_travel[Z_AXIS] = (-DEFAULT_Z_MAX_TRAVEL)};
+    .max_travel[Z_AXIS] = (-DEFAULT_Z_MAX_TRAVEL),
+    #ifdef HAS_DIGIPOTS
+    .current[X_AXIS] = DEFAULT_X_CURRENT,
+    .current[Y_AXIS] = DEFAULT_Y_CURRENT,
+    .current[Z_AXIS] = DEFAULT_Z_CURRENT,
+    #endif // HAS_DIGIPOTS
+};
 
 
 // Method to store startup lines into EEPROM
@@ -215,6 +221,12 @@ uint8_t settings_store_global_setting(uint8_t parameter, float value) {
             break;
           case 2: settings.acceleration[parameter] = value*60*60; break; // Convert to mm/min^2 for grbl internal use.
           case 3: settings.max_travel[parameter] = -value; break;  // Store as negative for grbl internal use.
+          #ifdef HAS_DIGIPOTS
+          case 4:
+            settings.current[parameter] = value;
+            set_current(parameter, settings.current[parameter]);
+            break;
+          #endif // HAS_DIGIPOTS
         }
         break; // Exit while-loop after setting has been configured and proceed to the EEPROM write call.
       } else {

grbl/settings.h

@@ -79,7 +79,11 @@
 // #define SETTING_INDEX_G92    N_COORDINATE_SYSTEM+2  // Coordinate offset (G92.2,G92.3 not supported)
 
 // Define Grbl axis settings numbering scheme. Starts at START_VAL, every INCREMENT, over N_SETTINGS.
+#ifdef HAS_DIGIPOTS
+#define AXIS_N_SETTINGS          5
+#else
 #define AXIS_N_SETTINGS          4
+#endif // HAS_DIGIPOTS
 #define AXIS_SETTINGS_START_VAL  100 // NOTE: Reserving settings values >= 100 for axis settings. Up to 255.
 #define AXIS_SETTINGS_INCREMENT  10  // Must be greater than the number of axis settings
 
@@ -90,6 +94,9 @@ typedef struct {
   float max_rate[N_AXIS];
   float acceleration[N_AXIS];
   float max_travel[N_AXIS];
+  #ifdef HAS_DIGIPOTS
+  float current[N_AXIS];
+  #endif // HAS_DIGIPOTS
 
   // Remaining Grbl settings
   uint8_t pulse_microseconds;