drv/ioport_lpf2: add boot power quirk

The city hub powers on the I/O ports (pin 4) during boot, so by the
time the device connection manager detected a UART device, in many
cases, it was too late to catch the device on the first sync. In the
case of the BOOST color distance sensor, this meant waiting 10 seconds
instead of 5 for the sensor to be ready.

This adds an option to enable a workaround for the quirk that cycles
power to the I/O ports immediately after boot. This is faster than
waiting for the next sync cycle.

Issue: pybricks/support#747

lib/pbio/drv/ioport/ioport_lpf2.c

@@ -466,15 +466,25 @@ PROCESS_THREAD(pbdrv_ioport_lpf2_process, ev, data) {
 
     PROCESS_BEGIN();
 
-    etimer_set(&timer, 2);
-
     for (int i = 0; i < PBDRV_CONFIG_IOPORT_LPF2_NUM_PORTS; i++) {
         init_one(i);
     }
 
+    // Some hubs turn on power to the I/O ports in the bootloader. This causes
+    // UART sync delays after boot. It is faster to power cycle the I/O devices
+    // than it is to wait for long sync in most cases.
+    #if PBDRV_CONFIG_IOPORT_LPF2_BOOT_POWER_QUIRK
+    pbdrv_gpio_out_low(&pbdrv_ioport_lpf2_platform_data.port_vcc);
+
+    etimer_set(&timer, 500);
+    PROCESS_WAIT_EVENT_UNTIL(ev == PROCESS_EVENT_TIMER && etimer_expired(&timer));
+    #endif
+
     // Turn on power on pin 4 on all ports
     pbdrv_gpio_out_high(&pbdrv_ioport_lpf2_platform_data.port_vcc);
 
+    etimer_set(&timer, 2);
+
     for (;;) {
         PROCESS_WAIT_EVENT();
 

lib/pbio/platform/city_hub/pbdrvconfig.h

@@ -48,6 +48,7 @@
 #define PBDRV_CONFIG_IOPORT                         (1)
 #define PBDRV_CONFIG_IOPORT_LPF2                    (1)
 #define PBDRV_CONFIG_IOPORT_LPF2_NUM_PORTS          (2)
+#define PBDRV_CONFIG_IOPORT_LPF2_BOOT_POWER_QUIRK   (1)
 #define PBDRV_CONFIG_IOPORT_LPF2_FIRST_PORT         PBIO_PORT_ID_A
 #define PBDRV_CONFIG_IOPORT_LPF2_LAST_PORT          PBIO_PORT_ID_B