From 66b662fc71061e874bef879820112b397f04e746 Mon Sep 17 00:00:00 2001
From: Bluebie <a@creativepony.com>
Date: Thu, 4 Oct 2012 13:59:25 +1000
Subject: Added low power mode, for chips which need to start with clkdiv8 and
 only switch to 16.5mhz when usb connection is detected somehow.

---
 firmware/main.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

(limited to 'firmware/main.c')

diff --git a/firmware/main.c b/firmware/main.c
index 08ec1db..62097b8 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -375,12 +375,26 @@ static inline void leaveBootloader(void) {
 
 int __attribute__((noreturn)) main(void) {
     /* initialize  */
+    #ifdef RESTORE_OSCCAL
+        uint8_t osccal_default = OSCCAL;
+    #endif
+    #if (!SET_CLOCK_PRESCALER) && LOW_POWER_MODE
+        uint8_t prescaler_default = CLKPR;
+    #endif
+    
     wdt_disable();      /* main app may have enabled watchdog */
     tiny85FlashInit();
     bootLoaderInit();
     
     
-    if (bootLoaderCondition()) {
+    if (bootLoaderStartCondition()) {
+        #if LOW_POWER_MODE
+            // turn off clock prescalling - chip must run at full speed for usb
+            // if you might run chip at lower voltages, detect that in bootLoaderStartCondition
+            CLKPR = 1 << CLKPCE;
+            CLKPR = 0;
+        #endif
+        
         initForUsbConnectivity();
         do {
             usbPoll();
@@ -404,6 +418,21 @@ int __attribute__((noreturn)) main(void) {
         } while(bootLoaderCondition());  /* main event loop runs so long as bootLoaderCondition remains truthy */
     }
     
+    // set clock prescaler to desired clock speed (changing from clkdiv8, or no division, depending on fuses)
+    #if LOW_POWER_MODE
+        #ifdef SET_CLOCK_PRESCALER
+            CLKPR = 1 << CLKPCE;
+            CLKPR = SET_CLOCK_PRESCALER;
+        #else
+            CLKPR = 1 << CLKPCE;
+            CLKPR = prescaler_default;
+        #endif
+    #endif
+    
+    // slowly bring down OSCCAL to it's original value before launching in to user program
+    #ifdef RESTORE_OSCCAL
+        while (OSCCAL > osccal_default) { OSCCAL -= 1; }
+    #endif
     leaveBootloader();
 }
 
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