7LikesFrame rate testing
01-23-2023 | 06:11 AM
#16
Joined: Mar 2011
Posts: 6,410
From: Austin,TX
Sky RC offers a 5 in 1 card with a PPM which I have used to compare frame rates of several systems in the past:
https://www.aliexpress.us/item/3256802923192804.html
I recall having to do some conversions to get the readings into Hz and can't find the thread where I posted my results, but I recall comparing Fly Sky with Radiopost and KO Propo systems that I had at the time. I found it interesting to see the knock off Rx's where about 25% slower frame rates. Various models of Rx's from the same brand also differed in frame rates too!
*** I found the link to my PPM thread but it was on RCFiles which was retired a couple years ago
https://www.aliexpress.us/item/3256802923192804.html
I recall having to do some conversions to get the readings into Hz and can't find the thread where I posted my results, but I recall comparing Fly Sky with Radiopost and KO Propo systems that I had at the time. I found it interesting to see the knock off Rx's where about 25% slower frame rates. Various models of Rx's from the same brand also differed in frame rates too!
*** I found the link to my PPM thread but it was on RCFiles which was retired a couple years ago
01-23-2023 | 02:49 PM
#17
There's another factor not many people consider in the SSR vs SHR debate. Microcontrollers have a finite timer resolution. I built a USB dongle adapter for VRC Pro using an Arduino, which by default has a 4us resolution on the timer function in the standard code library. I wrote a custom timer that knocks the resolution down to 0.5us. The SHR range is 1000-2000us, a 4us resolution means there are 250 steps between the min and max values. Each step has an error of 0.4%. SSR has a range between 50us and 550us, which means a 4us resolution has 125 steps, with an error of 0.8%.
Even when switching to the 0.5us timer in my code, there was still quite a bit of jitter in the recorded interval in SSR mode. It was visible in the software calibration screen. That suggests that the interrupts of the micro weren't consistently firing on time, or the signal from the receiver itself had some timing resolution errors. An oscilloscope would be able to verify the latter, which I don't have access to.
Even when switching to the 0.5us timer in my code, there was still quite a bit of jitter in the recorded interval in SSR mode. It was visible in the software calibration screen. That suggests that the interrupts of the micro weren't consistently firing on time, or the signal from the receiver itself had some timing resolution errors. An oscilloscope would be able to verify the latter, which I don't have access to.
Putting some numbers to the end-to-end latency would be super cool.
01-30-2023 | 04:28 PM
#20
Tech Fanatic
Joined: Apr 2007
Posts: 825
From: Overseas
Yes to my surprise the Futaba has overtaken Sanwa with the 10px with UR mode. I can confirm this as we put the 10px on our digital oscilloscope over the weekend as well as our Sanwa m17. Both over 1000hz, so we'll have to do a firmware update and a few minor modifications to our current design to support these modes.
1666hz is a bit more accurate for UR mode VS 1538hz for the SXR. MIN, MID, MAX UR mode below. Have a good one.
1666hz is a bit more accurate for UR mode VS 1538hz for the SXR. MIN, MID, MAX UR mode below. Have a good one.
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
