getMode()

Author: mestrode

src/TJA1020.cpp

@@ -44,7 +44,7 @@ void Lin_TJA1020::setMode(const Mode mode)
 {
     // we don't need to act, if we're allready there
     // see "setMode(sleep)" in the switch below
-    if (mode == _currentMode)
+    if (mode == getMode())
     {
         return;
     }
@@ -103,7 +103,7 @@ void Lin_TJA1020::setMode(const Mode mode)
     default: // = Sleep
         // no direct step from Standby to Sleep, but we don't know if we're in
         // we're going over _writingSlope
-        setMode(_writingSlope);
+        setMode(Mode::NormalSlope);
 
         // rising edge on /SLP while TXD = 1
         digitalWrite(txPin, HIGH);
@@ -131,12 +131,30 @@ void Lin_TJA1020::setMode(const Mode mode)
     }
 } // void Lin_TJA1020::setMode(TJA1020_Mode newMode)
 
-/// Defines standard slope, to be used, when writing to the bus
-void Lin_TJA1020::setSlope(const Mode slope)
+Lin_TJA1020::Mode Lin_TJA1020::getMode()
 {
-    _writingSlope = slope;
-    if (_writingSlope == Mode::Sleep)
-    {
-        _writingSlope = Mode::NormalSlope;
+    if (_currentMode == Mode::Sleep) {
+
+        // test MCU PullUp against TJA Pulldown
+        pinMode(txPin, INPUT);
+        delayMicroseconds(1); // settle time
+        bool hasWeakPullDn = !digitalRead(txPin);
+
+        pinMode(txPin, INPUT_PULLUP);
+        delayMicroseconds(1); // settle time
+        bool hasStrongPullDn = !digitalRead(txPin);
+
+        // revert setting
+        pinMode(txPin, INPUT);
+
+        if (hasWeakPullDn && !hasStrongPullDn)
+        {
+            // TXD has weak pull-down on remote wake-up
+            _currentMode = Mode::StandbyWakeupRemote;
+        } else {
+            // TXD has strong pull-down on local wake-up (caused by /WAKE pin)
+            _currentMode = Mode::StandbyWakeupLocal;
+        }
     }
+    return _currentMode;
 }

src/TJA1020.hpp

@@ -6,7 +6,7 @@
 //
 // Requires class Lin_Interface: https://github.com/mestrode/Lin-Interface-Library
 //
-// Tested with ESP32
+// Datasheet TJA1020: https://www.nxp.com/docs/en/data-sheet/TJA1020.pdf
 
 #pragma once
 
@@ -24,8 +24,27 @@ class Lin_TJA1020 : public HardwareSerial
     enum class Mode
     {
         Sleep,
+        // after Power on or setMode(Sleep)
+    // NSLP TXD (OUTPUT)                       RXD      INH      TRANSMITTER  REMARKS
+    // 0    weak pull-down                     floating floating off          no wake-up request detected
+    //                                                                        TERM = high-ohmic
+
         NormalSlope,
-        LowSlope
+    // NSLP TXD (OUTPUT)                       RXD      INH      TRANSMITTER
+    // 1    weak pull-down                     active   HIGH     normal slope TERM = 30k
+
+        LowSlope,
+    // NSLP TXD (OUTPUT)                       RXD      INH      TRANSMITTER
+    // 1    weak pull-down                     active   HIGH     low slope    TERM = 30k
+
+        StandbyWakeupRemote,
+        StandbyWakeupLocal
+    // NSLP TXD (OUTPUT)                       RXD      INH      TRANSMITTER  REMARKS
+    // 0    weak pull-down if remote wake-up;  LOW      HIGH     off          wake-up request detected;
+    //      strong pull-down if local wake-up;                                in this mode the microcontroller
+    //      note 2                                                            can read the wake-up source:
+    //                                                                        remote or local wake-up
+    //                                                                        TERM = 30k
     };
 
     /// provides HW-Lin Interface via TJA1020 Chip
@@ -37,13 +56,10 @@ class Lin_TJA1020 : public HardwareSerial
     /// switches the operational mode of TJA1020 chip
     /// @param mode target mode
     void setMode(const Mode mode);
-    /// Defines standard slope rate, when using to the bus
-    /// @param slope "NormalSlope" or "LowSlope" is only valid
-    void setSlope(const Mode slope);
+    Mode getMode();
 
 private:
-    Mode _writingSlope = Mode::NormalSlope;
-    Mode _currentMode = Mode::Sleep;
+    Mode _currentMode = Mode::Sleep; // after power on
     int8_t txPin;
     int8_t nslpPin;
 };