Embedded Technology
Figure 3. The higher precision of embOS-Ultra means programmed delays are actually kept to (with system tick interrupts issues no longer being problematic)
"PERFECT 7"
Figure 4: embOS-Ultra allows the processing element to stay in energy-saving mode for substantially longer, being woken up fewer times by interrupts
scheduling resolution. Instead of relying on the conventional system tick, embOS-Ultra internally uses clock cycles for all operations. Time-based operations, such as for task delays or software timers (which previously took up multiple ticks), may now be specifi ed in clock cycles. In addition, users can employ system-independent, high-resolution units (like µs or even ns) for time-based operations in the same application.
The cycle-resolution scheduling capabilities of embOS-Ultra have two key upshots. These are higher degrees of precision and signifi cantly lower energy consumption. Let’s look at each of them in turn.
First, cycle-resolution scheduling means that temporal sequences become more accurate. In most RTOSs, a Delay_ms(5) will interrupt the operation of the corresponding thread for approximately 4-5 ms - depending on how far away the next tick of the system is. This is due to the fact that a programmed delay cannot end between two system tick interrupts. It can only occur when there is a new system tick interrupt, which then triggers the scheduler (see Figure 3). Therefore, tasks that are to be interrupted for a period shorter than a system tick can only achieve this by actively waiting via polling of the hardware timer until the desired period has elapsed. In embOS-Ultra, a Delay_ms(5) will result in exactly 5ms interruption time.
Achieving lower power budgets is one of the prime objectives for any MCU vendor - and now the choice of RTOS can have a real
www.cieonline.co.uk
impact in this respect. Even if there is only one thread executing for several consecutive system ticks, the system tick interrupt will still occur periodically. This will mean that computing time is not utilised effi ciently (as described in Figure 4). In addition, the status of the processor core must also be saved to the stack beforehand and then restored, which wastes further computing time. Also, it should be noted that a CPU that is in energy-saving mode when no threads are being executed must be switched back to active mode each time in order to execute the interrupt service routine - thereby, once again, using up computing time and needlessly expending energy. With embOS-Ultra, the processing element simply stays in energy- saving mode longer - only being woken up when there is a task to execute. embOS-Ultra is available for many processor and compiler combinations, such as ARM Cortex-A/R/M and RISC-V. There are also a multitude of board support packages for different devices, plus evaluation hardware too.
Conclusion
The introduction of next generation RTOS technology is set to bring clear advantages to embedded systems. Through its implementation not only will higher precision be made possible, but also elevated levels of energy effi ciency will be delivered.
www.segger.com Components in Electronics March 2023 25
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62
