Hi
See the EVK ARM source code attachéd. eg chapter 6. 6 RANGING ALGORITHM.
But could I ask what revision of APS013 you have? Version 2.0 (and higher) is all about asymmetric TWR

thank you for replying. The documents did not answer my question though: What is the idea behind the asymmetric formula?

I am not asking about the ranging protocol - I am only asking about the formula.
I understand that the formula is displayed on page 19 of the EVK ARM source code guide and on page 4 of APS013.

But the only explanation is:
“Figure 11 shows this exchange and gives the formula used in the calculation of the range”

Where does the formula come from? Why does it work? Is there any literature?

Thanks.

PS: I am using version 2.2 of APS13, which is the same as your version 2.3 besides the new logo/layout.