From e4f7fd910c17d9c27136f0bbea1c7443f12cc111 Mon Sep 17 00:00:00 2001
From: Damjan Adamic <projectkk2glider@gmail.com>
Date: Fri, 28 Aug 2015 17:58:28 +0200
Subject: [PATCH] Fixes #2790: power on/off lop if big VCC capcitor was used

---
 radio/src/loadboot.cpp                 | 29 +++++++++++++++++----
 radio/src/targets/taranis/pwr_driver.c | 36 ++++++++++++--------------
 2 files changed, 40 insertions(+), 25 deletions(-)

diff --git a/radio/src/loadboot.cpp b/radio/src/loadboot.cpp
index f71fbd520..affa37fd6 100644
--- a/radio/src/loadboot.cpp
+++ b/radio/src/loadboot.cpp
@@ -100,13 +100,19 @@ void _bootStart()
   __ASM volatile ("nop");
   __ASM volatile ("nop");
 
-  // Turn soft power ON now
-  GPIOD->BSRRL = 1;                                  // set PWR_GPIO_PIN_ON pin to 1
-  GPIOD->MODER = (GPIOD->MODER & 0xFFFFFFFC) | 1;    // General purpose output mode
+  // Turn soft power ON now, but only if we got started because of the watchdog
+  // or software reset. If the radio was started by user pressing the power button
+  // then that button is providing power and we don't need to enable it here.
+  //
+  // If we were to turn it on here indiscriminately, then the radio can go into the 
+  // power on/off loop after being powered off by the user. (issue #2790)
+  if (WAS_RESET_BY_WATCHDOG_OR_SOFTWARE()) {
+    GPIOD->BSRRL = 1;                                  // set PWR_GPIO_PIN_ON pin to 1
+    GPIOD->MODER = (GPIOD->MODER & 0xFFFFFFFC) | 1;    // General purpose output mode
+  }
 
   // TRIMS_GPIO_PIN_LHR is on PG0 on 9XE and on PE3 on Taranis
   // TRIMS_GPIO_PIN_RHL is on PC1 on all versions
-
   // turn on pull-ups on trim keys 
   GPIOC->PUPDR = 0x00000004;
 #if defined(REV9E)
@@ -114,11 +120,24 @@ void _bootStart()
 #else
   GPIOE->PUPDR = 0x00000040;
 #endif
-  
+
+  // wait for inputs to stabilize
   for (uint32_t i = 0; i < 50000; i += 1) {
     bwdt_reset();
   }
 
+  // now the second part of power on sequence
+  // If we got here and the radio was not started by the watchdog/software reset,
+  // then we must have a power button pressed. If not then we are in power on/off loop
+  // and to terminate it, just wait here without turning on PWR pin. The power supply will
+  // eventually exhaust and the radio will turn off.
+  if (!WAS_RESET_BY_WATCHDOG_OR_SOFTWARE()) {
+    // wait here until the power key is pressed
+    while (GPIOD->IDR & PWR_GPIO_PIN_SWITCH) {
+      bwdt_reset();
+    }
+  }
+
   if (!(TRIMS_GPIO_REG_LHR & TRIMS_GPIO_PIN_LHR) && !(TRIMS_GPIO_REG_RHL & TRIMS_GPIO_PIN_RHL)) {
     // Bootloader needed
     const uint8_t *src;
diff --git a/radio/src/targets/taranis/pwr_driver.c b/radio/src/targets/taranis/pwr_driver.c
index 1d2038a5d..6ad746999 100644
--- a/radio/src/targets/taranis/pwr_driver.c
+++ b/radio/src/targets/taranis/pwr_driver.c
@@ -87,29 +87,25 @@ void pwrOff()
   // disable interrupts
  __disable_irq();
 
-
-#if defined(REV9E)
-  // 9E needs watchdog reset because CPU is still running while 
-  // the power key is held pressed by the user.
-  // The power key should be released by now, but we must make sure
-  while (pwrPressed()) {
-    wdt_reset();
-  }
-  // Put the CPU into sleep to reduce the consumption,
-  // it might help with the RTC reset issue
-  PWR->CR |= PWR_CR_CWUF;
-  /* Select STANDBY mode */
-  PWR->CR |= PWR_CR_PDDS;
-  /* Set SLEEPDEEP bit of Cortex System Control Register */
-  SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
-  /* Request Wait For Event */
-  __WFE();
-#endif
-
   while(1) {
     wdt_reset();
+#if defined(REV9E)
+    // 9E needs watchdog reset because CPU is still running while 
+    // the power key is held pressed by the user.
+    // The power key should be released by now, but we must make sure
+    if (!pwrPressed()) {
+      // Put the CPU into sleep to reduce the consumption,
+      // it might help with the RTC reset issue
+      PWR->CR |= PWR_CR_CWUF;
+      /* Select STANDBY mode */
+      PWR->CR |= PWR_CR_PDDS;
+      /* Set SLEEPDEEP bit of Cortex System Control Register */
+      SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
+      /* Request Wait For Event */
+      __WFE();
+    }
+#endif
   }
-
   //this function must not return!
 }