fixes

avr_code/power_mgmt.c

@@ -1,15 +1,25 @@
+// One-shot clock gating for every peripheral this firmware never uses (and
+// the ADC, which adc_Enable()/adc_Disable() power up only around a reading).
+// In use and left alone: SPI1 (radio + EEPROM), TWI0 (RTC + NFC tag), and
+// USART0 when serial logging is compiled in.
+
 #include "power_mgmt.h"
 
 void shutdown_all_peripherals(void)
 {
-
     power_adc_disable();
     power_timer0_disable();
     power_timer1_disable();
     power_timer2_disable();
     power_timer3_disable();
+    power_usart1_disable();
+#ifdef power_spi0_disable
+    power_spi0_disable();
+#endif
+#ifdef power_twi1_disable
+    power_twi1_disable();
+#endif
 #if !DO_UART
     power_usart0_disable();
-    power_usart1_disable();
 #endif
 }