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Added code to demonstrate use of new I2C timeout feature #356

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Added code to demonstrate use of new I2C timeout feature #356

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ae3dd32
Added code to demonstrate use of new I2C timeout feature
paynterf Jul 11, 2020
8aa1cef
Move anti-lockup code to beginning of Setup()
paynterf Jul 16, 2020
b9a9ab3
Remove 'clearWireTimeoutFlag()' from setup. It is explicitly cleared…
paynterf Jul 16, 2020
cf81cfc
Add check for WIRE_HAS_TIMEOUT
matthijskooijman Sep 26, 2020
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16 changes: 16 additions & 0 deletions libraries/Wire/examples/i2c_scanner/i2c_scanner.ino
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,8 @@
// A sensor seems to use address 120.
// Version 6, November 27, 2015.
// Added waiting for the Leonardo serial communication.
// Version 6, July 10, 2020 by G. Frank Paynter
// Demonstrates the use of the new Wire library timeout feature
//
//
// This sketch tests the standard 7-bit addresses
Expand All @@ -29,15 +31,29 @@

#include <Wire.h>

uint16_t wireTimeoutCount; //capture I2C bus timeout events

void setup() {
Wire.begin();

Serial.begin(9600);
while (!Serial); // Leonardo: wait for serial monitor
Serial.println("\nI2C Scanner");

Wire.setWireTimeout(3000, true); //timeout value in uSec, true to reset I2C bus on timeout
wireTimeoutCount = 0;
Wire.clearWireTimeoutFlag();
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Why not put this directly after the Wire.begin()? Seems more clear? Also, is clearing the timeout flag really needed here? We can rely on it being cleared on startup, I think? Same for initializing the count to 0, why not just do that in the variable declaration?

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Thanks for the comment; I moved the anti-lockup code to just under 'Wire.begin()' as you suggested. I wanted to put the timeout flag in to expose its existence to a new user; otherwise they might never know the timeout flag existed at all or how to query it.

I could initialize the variable in the declaration, but I have learned that assuming a variable has been initialized to zero 'somewhere else' can lead to confusing/incorrect behavior. I like making things obvious and explicit, even at the cost of an extra line or two of code. YMMV ;-).

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I wanted to put the timeout flag in to expose its existence to a new user; otherwise they might never know the timeout flag existed at all or how to query it.

Yeah, that's fine (and I think this might be a good example for it), I was just suggesting not doing the timeout flag handling in all examples (OTOH, maybe it should be).

I like making things obvious and explicit, even at the cost of an extra line or two of code. YMMV ;-).

It does (on this particular thing, I do like explicit in general, but also concise), but it's ok :-)

What about (not) calling clearWireTimeoutFlag() on startup? You've now added a comment that seems less than helpful?

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Good catch! I removed the call to clearWireTimeoutFlag() as it is explicitly cleared in Wire.setWireTimeout()


}

void loop() {
if (Wire.getWireTimeoutFlag())
{
wireTimeoutCount++;
Wire.clearWireTimeoutFlag();
Serial.print("Wire timeout detected; count now "); Serial.println(wireTimeoutCount);
}

int nDevices = 0;

Serial.println("Scanning...");
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