drivers/dht: Allow open-drain-high call to be DHT specific if needed.

Some ports (eg esp8266) need to have specific behaviour for driving a DHT
reliably.

drivers/dht/dht.c

@@ -32,6 +32,11 @@
 #include "extmod/machine_pulse.h"
 #include "drivers/dht/dht.h"
 
+// Allow the open-drain-high call to be DHT specific for ports that need it
+#ifndef mp_hal_pin_od_high_dht
+#define mp_hal_pin_od_high_dht mp_hal_pin_od_high
+#endif
+
 STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
     mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(pin_in);
     mp_hal_pin_open_drain(pin);
@@ -44,7 +49,7 @@ STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
     }
 
     // issue start command
-    mp_hal_pin_od_high(pin);
+    mp_hal_pin_od_high_dht(pin);
     mp_hal_delay_ms(250);
     mp_hal_pin_od_low(pin);
     mp_hal_delay_ms(18);
@@ -52,7 +57,7 @@ STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
     mp_uint_t irq_state = mp_hal_quiet_timing_enter();
 
     // release the line so the device can respond
-    mp_hal_pin_od_high(pin);
+    mp_hal_pin_od_high_dht(pin);
     mp_hal_delay_us_fast(10);
 
     // wait for device to respond