Metaboard/2010 activities/6-pin auto-detecting programming: Unterschied zwischen den Versionen

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@@ Zeile 33: / Zeile 33: @@
 When idling, RESET is actively pulled low, and POWER is configured as input with the builtin pullup resistor. Thus, connecting a sensor regularly or flipped pulls POWER down and a device is recognized.
-After the presence of a plug is detected, it can be determined whether the direction is ok. A simple implementation works by configuring POWER as an output and driving it high, then reading on RESET, but this could create problems if POWER just got short-circuited to ground; an enhanced solution that includes using MISO / MOSI SCK is being worked on. (Those pins can be used freely for a short time, in which the other slaves on the bus are disabled.)
+After the presence of a plug is detected, it can be determined whether the direction is ok by setting RESET as input with pullup. If POWER goes up again, the connector is plugged in the wrong way, otherwise the system can be powered.
+Here is an example of how to poll for the connector:
+ #define RESET 9
+ #define POWER 10
+ #define MISO 12
+ #define MOSI 11
+ #define SCK 13
+ void reset() {
+ 	digitalWrite(RESET, LOW);
+ 	pinMode(RESET, OUTPUT);
+ 	pinMode(POWER, INPUT);
+ 	digitalWrite(POWER, HIGH);
+ }
+ void setup() {
+ 	reset();
+ 	pinMode(MISO, INPUT);
+ 	pinMode(MOSI, INPUT);
+ 	pinMode(SCK, INPUT);
+ 	digitalWrite(MISO, HIGH);
+ 	digitalWrite(MOSI, HIGH);
+ 	digitalWrite(SCK, HIGH);
+ 	Serial.begin(19200);
+ }
+ void loop() {
+ 	if(digitalRead(POWER) != LOW) {
+ 		Serial.write("Nothing detected on power line, allowing other SPI communication\r\n");
+ 		while(digitalRead(POWER) != LOW); // blocking in the poll is nothing we normally want; using it here to supress duplicate messages
+ 	}
+ 	Serial.write("Detected something\r\n");
+ 	pinMode(RESET, INPUT);
+ 	digitalWrite(RESET, HIGH);
+ 	if(digitalRead(POWER) == HIGH) {
+ 		Serial.write("Match was bad\r\n");
+ 	} else {
+ 		Serial.write("Match was GOOD!\r\n");
+ 		Serial.write("Waiting for confirmation.\r\n");
+ 		int bad = 0;
+ 		for(int i=0; i < 20; ++i) {
+ 			delay(1);
+ 			if(digitalRead(POWER) == HIGH)
+ 			{
+ 				bad = 1;
+ 				break;
+ 			}
+ 		}
+ 		if(bad == 0) {
+ 			Serial.write("Confirmed, taking up the chip.\r\n");
+ 			pinMode(RESET, OUTPUT);
+ 			digitalWrite(RESET, HIGH);
+ 			pinMode(POWER, OUTPUT);
+ 			digitalWrite(POWER, HIGH);
+ 			delay(10000);
+ 			Serial.write("enough\r\n");
+ 		} else
+ 			Serial.write("Unconfirmed, returning\r\n");
+ 	}
+ 	delay(200);
+ 	reset();
+ }
+Note that for polling to work in practice, the digitalWrite({MOSI, SCK}, HIGH) might have to be set before polling.