[STM32F4] Communication betwenn 2 tasks

kronanberg wrote on Friday, February 10, 2012:


I 'm learning to use FreeRTOS and I ask myself a question on the communication between 2 task.

In my example, I realise an analog to digital converter on one pin every 100 ms and I send this resultat in a queue.

An other task receives this information by the queue and transmits it at hyperterminal (via UART) every 500 ms.

The problem is that the transmitted data is not the last sampled data.

What is the solution to communicate when 2 tasks don’t work at the same frequency ?



richard_damon wrote on Friday, February 10, 2012:

If task2 just wants the “last” value converted, the best choice is for the data source to just put the value in a global variable and the second task to read from that.

The idea of a queue is to allow a task to wait for data, and to startup as soon as it is available, or if the queue gets full, for the generating task to be delayed, and restarted as soon as there is space to place the data.

Both ends of a queue by definition work at the same average rate, otherwise the queue overflows or underflows.