topic KV5x: How to connect the encoder inputs to a general purpose timer? in Kinetis Microcontrollers

KV5x: How to connect the encoder inputs to a general purpose timer?

arimendes — Fri, 26 Aug 2016 11:55:33 GMT

Hi,

Section 47.2.1 of the KV5x Reference Manual states that "Inputs can be connected to a general purpose timer to aid low speed velocity". How can it be done if there is only one input capture connected to a XBARA outuput( XBARA_OUT42)?

Ari.

Re: KV5x: How to connect the encoder inputs to a general purpose timer?

egoodii — Fri, 26 Aug 2016 15:06:26 GMT

High-speed velocity is easily determined as 'counts per interval', but low-speed is best measured by looking at pulse-width. The two encoder lines will ALWAYS have the same pulse widths (just interleaved!), so it is sufficient to hook just one to a timer-capture input to give you clock-counts-between-edges as pulse-width, the inverse of velocity.

Re: KV5x: How to connect the encoder inputs to a general purpose timer?

xiangjun_rong — Mon, 29 Aug 2016 04:08:12 GMT

Hi, Ari,

For KV5X, you have to connect the encoder signals ENC_PHA and ENC_PHB to XB_INx for example XB_IN2 and XB_IN3 and use crossbar to route them to XBARA_OUT44(ENC_PHA) and XBARA_OUT45(ENC_PHB), at the same time route one of them to XBARA_OUT42 which is FTM1_CH1, you can set up the FTM1_CH1 in capture mode so that you can test the cycle or pulse width of FTM1_CH1 with high frequency ticks when the motor is in low speed mode as EARL GOODRICH said.

Pls refer to section 29.1.2 XBARA signal output assignment.

If your motor do not works in low speed, the connection to FTM1_CH1 is unnecessary.

Hope it can help you.

XiangJun Rong

Re: KV5x: How to connect the encoder inputs to a general purpose timer?

arimendes — Thu, 01 Sep 2016 01:09:35 GMT

Hi, thanks for your tips.

I tested as Xianjun suggested and it worked well. I also used the XBARB and AOI moudules to do XOR logic of the XB_IN2 and XB_IN3 inputs and output it do the FTM1_CH1 input capture using the XBARA. It was useful to reduce the response time of velocity measurements in low speed.

Thanks.

Ari.