Add startFPGA weak hook to allow bitstream autostart

Author: facchinm

variants/mkrvidor/variant.cpp

@@ -215,6 +215,7 @@ void initVariant() {
 #if defined(USE_BQ24195L_PMIC)
   enable_battery_charging();
 #endif
+  startFPGA();
 }
 
 void enableFpgaClock() {
@@ -231,6 +232,8 @@ void disableFpgaClock() {
   delay(1000);
 }
 
+ __attribute__ ((weak)) void startFPGA() {};
+
 // Multi-serial objects instantiation
 SERCOM sercom0(SERCOM0);
 SERCOM sercom1(SERCOM1);

variants/mkrvidor/variant.h

@@ -199,11 +199,12 @@ extern Uart Serial1;
 // Alias Serial to SerialUSB
 #define Serial                      SerialUSB
 
-// FPGA-specific clock
+// FPGA-specific functions
 #ifdef __cplusplus
 extern "C" {
 #endif
 void clockout(uint32_t gclk, int32_t divisor);
+void startFPGA();
 #ifdef __cplusplus
 }
 #endif