I’m having a rather odd issue with the temperature sensor bing used in a timer callback. If the temperature callback function is executed in the loop everything works perfectly. However, if the the callback is executed by the timer, the sensor always reads -127. I have no idea why this could happ…

Timers behave like interrupts and should thus be kept as short as possible. Use them to set flags to act upon in the loop, but don’t do any time consuming tasks in them (calling other functions).

Ok, thanks. I used a mills timer in my check temp function (i dont need extream accuracy). are there any tech details on how timers and interupts work exactly? Im trying to create a non-blocking loop so that buttons have a snappy response. My other timer sends two Particle.publish commands and th…

If you want snappy button response, you can use interrupts for them. And the reason for the bad readings might be that the OneWire communication doesn’t play well with the seperate thread for timers.

Thanks @ ScruffR. I am using an interrupt for the button but there still seems to be a delay at times which i assumed was during a temp check cycle. So i tried the timer implementation, i assumed it was threaded. Moving the temp check to the timer did solve the random delay issue, but as noted th…

@arctelix , this is a tough one. Software timers on the Photon are implemented using FreeRTOS software timers. All timers run in a shared thread, separate from the user app thread. Since the timers share the same thread, within that thread the run “round robin” style meaning when a timer fires, it…

@peekay123 thanks for the reply. getTime() is just a string time stamp for the OLED output, its not used as a time based function at all. String getTime() { String h = String(Time.hour()); String m = String(Time.minute()); String s = String(Time.second()); return h+":"+m+":"+s; }

You might want to use Time.format("%H:%M:%S") or just Time.format("%T") See http://www.cplusplus.com/reference/ctime/strftime/

@arctelix , @ScruffR , I ran some tests yesterday using the timer callback for reading the ds18b20 temperature. I streamlined the code to remove String operations in the callback and added some counters to keep track of total and bad readings from the sensor. All tests were compiled on Build with a …

Temperatur sensor function fails with timer, works fine in loop

Troubleshooting

chrisb2 October 12, 2016, 6:13am 5

Assuming they work like interrupts then any global variables you are setting inside the interrupt and reading outside it in the loop, or in your publishTemp function might need to be declared volatile, see:

EMBED WITH ELLIOT: THE VOLATILE KEYWORD

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Temperatur sensor function fails with timer, works fine in loop

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