NXP Semiconductors KL25 Series - KL25 Sub-Family Reference Manual, Rev. 3, September

The vmid voltage is defined as V(vmid) = (V(vp) + V(vm))/2.
The Rs value is defined by i_ext_3v<2:0> register bits.
Figure 42-15. TSI circuit in noise detection mode
To determine the noise level the below algorithm can be used:
1. Initialize Rs = maxrs; Dvolt = minDv (set other configurations also)
2. Perform a noise cycle.
3. If TSIcounter < 3, go to step 8
4. If Rs = minrs, go to step 6.
5. Reduce value of Rs. go to step 2
6. If Dvolt = maxDv, go to END
7. Increase value of Dvolt. Set Rs = maxrs. go to step 2
8. If Rs > minrs, (Reduce value of Rs, go to END)
9. Rs = maxrs, reduce value of Dvolt.
10. END Get value of Rs and Dvolt.
Chapter 42 Touch Sensing Input (TSI)
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 801