use tud_cdc_rx_cb to process serial data for xsbug sooner

Author: phoddie

build/devices/pico/base/debugger.c

@@ -47,6 +47,11 @@ void tud_cdc_line_state_cb(uint8_t itf, bool dtr, bool rts)
 	}
 	lastRTS = rts;
 }
+
+void tud_cdc_rx_cb(uint8_t itf)
+{
+	modMessagePostToMachineFromISR(NULL, (modMessageDeliver)fxReceiveLoop, NULL);
+}
 #endif
 
 //---------

xs/platforms/pico/xsHost.c

@@ -919,7 +919,7 @@ int modMessageService(xsMachine *the, int maxDelayMS)
 	while (msg && msg->marked) {
 		modMessage next;
 
-		if (msg->callback)
+		if (msg->callback && (!msg->the || (msg->the == the)))
 			(msg->callback)(msg->the, msg->refcon, msg->message, msg->length);
 
 		modCriticalSectionBegin();