Adapt BL to UNO WiFi rev2 internal UART

Author: facchinm

bootloaders/atmega4809_uart_bl.hex

@@ -1,15 +1,18 @@
-:100000001124109948C080EC80932608A0912311F8
-:100010000A2E000CBB0BBC5F2CE530E00E945200A6
-:10002000DC01CB019E5FAF4FBF4F2AE0B595A7958E
-:10003000979587952A95D1F780932808909329085A
-:100040008091E20584608093E205449A669A6E9AF4
-:10005000E0E0F1E49DE923E030E48091240887FFAB
-:10006000FCCF80912008809322088193AF014F77C5
-:100070005527452B51F494BF209300108091021016
-:1000800080FDFCCF8DB183278DB9309731F7E0E843
-:10009000F0E0099507C082E080930110E0E8F0E00D
-:1000A0000995B1CF0E945900B7FF0895821B930BA9
-:1000B0000895A29FB001B39FC001A39F700D811D41
-:1000C0001124911DB29F700D811D1124911D089561
+:10000000112480911F138B3E09F059C08FEF80930C
+:100010001F1393E08DE984BF90930010809102102C
+:1000200081FDFCCF80EC80930608A09123110A2E5D
+:10003000000CBB0BBC5F2CE530E00E946600DC01CD
+:10004000CB019E5FAF4FBF4F2AE0B595A79597951F
+:1000500087952A95D1F78093080890930908809195
+:10006000E20581608093E205049A669A9DB180E47E
+:1000700089278DB9E0E0F1E49DE923E030E4809147
+:10008000040887FFFCCF80910008809302088193C9
+:10009000AF014F775527452B51F494BF20930010A3
+:1000A0008091021080FDFCCF8DB183278DB93097F0
+:1000B00031F791E088ED84BF9093410007C082E062
+:1000C00080930110E0E8F0E00995ACCF0E946D004C
+:1000D000B7FF0895821B930B0895A29FB001B39FB1
+:1000E000C001A39F700D811D1124911DB29F700D41
+:0800F000811D1124911D0895EA
 :02000004008278
 :00000001FF

bootloaders/boot.c

@@ -29,10 +29,10 @@
  * to disable standard startup files in Toolchain->AVR/GNU Linker->General.
  *
  * The example is written for ATtiny817 with the following pinout:
- * USART0 TxD PB2
- * USART0 RxD PB3
- * LED0       PB4
- * SW1        PC5 (external pull-up)
+ * USART0 TxD PA4
+ * USART0 RxD PA5
+ * LED0       PD6
+ * SW1        PC1 (external pull-up)
  */
 #define F_CPU_RESET (16E6/6)
 
@@ -100,6 +100,8 @@ __attribute__((naked)) __attribute__((section(".ctors"))) void boot(void)
   init_uart();
   init_status_led();
 
+  toggle_status_led();
+
   /*
    * Start programming at start for application section
    * Subtract MAPPED_PROGMEM_START in condition to handle overflow on large flash sizes
@@ -131,11 +133,16 @@ __attribute__((naked)) __attribute__((section(".ctors"))) void boot(void)
  */
 static bool is_bootloader_requested(void)
 {
-  /* Check if SW1 (PA0) is low */
-  if(VPORTA.IN & PIN0_bm) {
-    return false;
+  /* Check for boot request from firmware */
+  if (USERROW.USERROW31 == 0xEB) {
+    /* Clear boot request*/
+    USERROW.USERROW31 = 0xff;
+    _PROTECTED_WRITE_SPM(NVMCTRL.CTRLA, NVMCTRL_CMD_PAGEERASEWRITE_gc);
+    while(NVMCTRL.STATUS & NVMCTRL_EEBUSY_bm);
+
+    return true;
   }
-  return true;
+  return false;
 }
 
 /*
@@ -144,7 +151,7 @@ static bool is_bootloader_requested(void)
 static void init_uart(void)
 {
   /* Configure UART */
-  USART1.CTRLB = USART_RXEN_bm | USART_TXEN_bm;
+  USART0.CTRLB = USART_RXEN_bm | USART_TXEN_bm;
 
   /* From datasheet:
    * Baud rate compensated with factory stored frequency error
@@ -157,35 +164,35 @@ static void init_uart(void)
   baud_reg_val *= (1024 + sigrow_val);    // sum resolution + error
   baud_reg_val += 512;                    // compensate for rounding error
   baud_reg_val /= 1024;                   // divide by resolution
-  USART1.BAUD = (int16_t) baud_reg_val;   // set adjusted baud rate
+  USART0.BAUD = (int16_t) baud_reg_val;   // set adjusted baud rate
 
-  PORTMUX.USARTROUTEA |= PORTMUX_USART1_ALT1_gc;
+  PORTMUX.USARTROUTEA |= PORTMUX_USART0_ALT1_gc;
 
-  /* Set TxD (PB2) as output */
-  VPORTC.DIR |= PIN4_bm;
+  /* Set TxD (PA4) as output */
+  VPORTA.DIR |= PIN4_bm;
 }
 
 static uint8_t uart_receive(void)
 {
   /* Poll for data received */
-  while(!(USART1.STATUS & USART_RXCIF_bm));
-  return USART1.RXDATAL;
+  while(!(USART0.STATUS & USART_RXCIF_bm));
+  return USART0.RXDATAL;
 }
 
 static void uart_send(uint8_t byte)
 {
   /* Data will be sent when TXDATA is written */
-  USART1.TXDATAL = byte;
+  USART0.TXDATAL = byte;
 }
 
 static void init_status_led(void)
 {
-  /* Set LED0 (PB4) as output */
+  /* Set LED0 (PD6) as output */
   VPORTD.DIR |= PIN6_bm;
 }
 
 static void toggle_status_led(void)
 {
-  /* Toggle LED0 (PB4) */
+  /* Toggle LED0 (PD6) */
   VPORTD.OUT ^= PIN6_bm;
 }