AP_Periph: use a longer loop delay on non-H7

the short delay broke the F412 based CUAV_GPS

Tools/AP_Periph/can.cpp

@@ -82,6 +82,15 @@ extern AP_Periph_FW periph;
 #define HAL_CAN_POOL_SIZE 4000
 #endif
 
+#ifndef HAL_PERIPH_LOOP_DELAY_US
+// delay between can loop updates. This needs to be longer on F4
+#if defined(STM32H7)
+#define HAL_PERIPH_LOOP_DELAY_US 64
+#else
+#define HAL_PERIPH_LOOP_DELAY_US 512
+#endif
+#endif
+
 #define DEBUG_PRINTS 0
 #define DEBUG_PKTS 0
 #if DEBUG_PRINTS
@@ -1623,7 +1632,7 @@ void AP_Periph_FW::can_update()
 #endif
     const uint32_t now_us = AP_HAL::micros();
     while ((AP_HAL::micros() - now_us) < 1000) {
-        hal.scheduler->delay_microseconds(64);
+        hal.scheduler->delay_microseconds(HAL_PERIPH_LOOP_DELAY_US);
         processTx();
         processRx();
     }