iMX7D: How to output 32K clock

[houshiyun]

Hello, we have an interphone project using MCIMX7D3EVK10SD with external 32.768KHz and 24MHz crystals. We want to make PWM pin of iMX7D output 32K clock to BT and audio codec. But our softwarer engineer don't know how to configure PWM pin. So we need your help.

1: Can PWM pin output 32K clock?

2: How can we check the external 32.768KHz crystal, working, or not?

Many thanks.

[igorpadykov]

Hi Hou

32K clock can be easily outputted using CLKO signals, please

check Table 5-11. Clock Root Table i.MX7D Reference Manual

http://cache.nxp.com/files/32bit/doc/ref_manual/IMX7DRM.pdf

For 2.) one can look at sect.4.3. Checking for clock pitfalls

Hardware Guide

https://www.nxp.com/docs/en/user-guide/IMX7DSHDG.pdf 

Best regards
igor
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[houshiyun]

Hi, igorpadykov

I see, CCM_CLKO2 can select OSC_32K clock source by configuring CCM_TARGET_ROOT register. But I don't find the CCM_CLKO2  pin of MCIMX7D3EVK10SD.

From table 5-10, IMX7DRM , the CCM_CLKO2 signal is at GPIO1_IO03 and SD1_WP. But I don't find the CCM_CLKO2 signal in PIN D2 and Y6 by Pins Tool V4.1. Please see attached photos.

So can you help me confirm it?

Many thanks.

[igorpadykov]

muxing options can be found in sect.8.1.1.1 Muxing Options

i.MX7D Reference Manual

http://cache.nxp.com/files/32bit/doc/ref_manual/IMX7DRM.pdf

Best regards
igor