Bug Fix

 From  ElTangas/jtag2updi:
The response generated by the JTAG2::enter_progmode() function was malformed in certain situations. This bug was silently ignored by avrdude, thus not detected until now. Thanks to @kosilin for detecting this.

JTAG2.cpp

@@ -86,10 +86,15 @@ void JTAG2::delay_exec() {
 }
 
 // *** Set status function ***
-void JTAG2::set_status(uint8_t status_code) {
+void JTAG2::set_status(response status_code) {
   packet.size_word[0] = 1;
   packet.body[0] = status_code;
 }
+void JTAG2::set_status(response status_code, uint8_t param) {
+    packet.size_word[0] = 2;
+    packet.body[0] = status_code;
+    packet.body[1] = param;
+}
 
 // *** General command functions ***
 
@@ -194,9 +199,9 @@ void JTAG2::enter_progmode() {
         break;
       }
       // At this point we need to check if the chip is locked, if so don't attempt to enter program mode
+      // This is because the previous chip reset may enable a lock bit that was just written (it only becomes active after reset).
       if (UPDI::CPU_mode<0x01>()) {
-        packet.body[0] = RSP_ILLEGAL_MCU_STATE;
-        packet.body[1] = system_status; // return system status (bit 0 will be set to indicate the MCU is locked)
+        set_status(RSP_ILLEGAL_MCU_STATE, system_status | 0x01); // return system status (bit 0 will be set to indicate the MCU is locked)
         break;
       }
       // Now we have time to enter program mode (this mode also disables the WDT)
@@ -243,8 +248,7 @@ void JTAG2::enter_progmode() {
       break;
     default:
       // If we're somehow NOT in programming mode now, that's no good - inform host of this unfortunate state of affairs
-      packet.body[0] = RSP_ILLEGAL_MCU_STATE;
-      packet.body[1] = system_status; // return whatever system status caused this error
+      set_status(RSP_ILLEGAL_MCU_STATE, system_status); // return whatever system status caused this error
   }
 }
 
@@ -276,9 +280,7 @@ void JTAG2::leave_progmode() {
       break;
     // in other modes fail and inform host of wrong mode
     default:
-      packet.size_word[0] = 2;
-      packet.body[0] = RSP_ILLEGAL_MCU_STATE;
-      packet.body[1] = system_status; // 0x01;
+      set_status(RSP_ILLEGAL_MCU_STATE, 0x01);
   }
 }
 
@@ -294,9 +296,7 @@ void JTAG2::go() {
   void JTAG2::read_mem() {
     if (UPDI::CPU_mode() != 0x08){
       // fail if not in program mode
-      packet.size_word[0] = 2;
-      packet.body[0] = RSP_ILLEGAL_MCU_STATE;
-      packet.body[1] = 0x01;
+       set_status(RSP_ILLEGAL_MCU_STATE, 0x01);
     }
     else {
       // in program mode
@@ -642,5 +642,3 @@ namespace {
     #endif
   }
 }
-
-

JTAG2.h

@@ -42,7 +42,7 @@ namespace JTAG2 {
     BAUD_256000,
     BAUD_512000,
     BAUD_1024000,
-    // Extension to jtagmkII protocol: extra baud rates, decimal series.
+    // Extension to jtagmkII protocol: extra baud rates, binary series.
     BAUD_150000,
     BAUD_200000,
     BAUD_250000,
@@ -55,7 +55,6 @@ namespace JTAG2 {
     BAUD_1500000,
     BAUD_2000000,
     BAUD_3000000,
-
     BAUD_LOWER = BAUD_2400,
     BAUD_UPPER = BAUD_3000000
   };
@@ -172,7 +171,8 @@ namespace JTAG2 {
   void delay_exec();
 
   // *** Set status function ***
-  void set_status(uint8_t) __attribute__ ((noinline));
+  void set_status(response) __attribute__ ((noinline));
+  void set_status(response, uint8_t) __attribute__ ((noinline));
 
   // *** General command functions ***
   void sign_on();