Add hall signal delay compensation

[at-wat]

fix #71
fix #38

[at-wat]

• calculate rely-hall velocity threshold from params

---

• interrupt interval (100us at default) and hall signal delay should be less than 0.5%(= 1.8deg) of hall sinal interval (e.g. 3000rpm = 50Hz -> 20ms)
  • hall sinal interval [cycle]: enc_rev [cnt] / vel [cnt/cycle]
  • interrupt interval [cycle]: control_cycle [ms] / ((48000 [kHz] / 2) / PWM_resolution)

interrupt interval [cycle] < hall sinal edge interval [cycle]
control_cycle [ms] / ((48000 [kHz] / 2) / PWM_resolution) < 0.005 * enc_rev [cnt] / vel [cnt/cycle]
vel < 0.005 * enc_rev [cnt] * ((48000 [kHz] / 2) / PWM_resolution) / control_cycle [ms]
vel < 0.005 * enc_rev [cnt] * 48000 [kHz] / (2 * PWM_resolution * control_cycle [ms])

[at-wat]

@seiga-k could you take a look this and also #73, #75, #76?

[seiga-k]

About #73

tfrog-motordriver/controlPWM.c

I feel const int tan is not good naming. How about const int tan_th or something?

Other

LGTM

[seiga-k]

About #75

LGTM

[seiga-k]

About #76

tfrog-motordriver/controlPWM.c

Is arm-gcc compiler promise a behavior of compile a modulo to less calculation method?

hall_pos = hall_pos % ENC0_BUF_MAX;

You limit ENC0_BUF_MAX as 2^n as bellow in tfrog-motordriver/controlVelocity.h.

// ENC0_BUF_MAX must be 2^n to reduce computation cost.
#define ENC0_BUF_MAX 64

So, how about like this?

const int enc0_buf_mask = ENC0_BUF_MAX - 1;
hall_pos &= enc0_buf_mask;

[at-wat]

Is arm-gcc compiler promise a behavior of compile a modulo to less calculation method?

I don't think bit mask is required as gcc don't use real modulo operation for immediate value divider, even if it is compiled with -O0.
I have added static assert to ensure it is power of two.