Linux/AM3358: PWM signal capture

Manimekala Rajendran

Part Number: AM3358

Tool/software: Linux

Hi,

I am using Beagle Bone Black with Wi-Fi cape. I want to connect sensor with the BBB and want to read the data from sensor. Sensor is sending output as PWM signal to the BBB.

How can I read the PWM signal in BBB? Which pin I have to use?

Can you please suggest any solution?

Thanks in advance.

Regards,

Manimekala Rajendran.

over 6 years ago

0 Yordan Kovachev over 6 years ago

TI__Guru**** 161600 points

Can you tell me what sensor is this? If possible share its datasheet to see what is the best way to connect it to BBB.

Best Regards,
Yordan

0 Manimekala Rajendran over 6 years ago in reply to Yordan Kovachev

Intellectual 370 points

Hi Yordan,

Thank you for your prompt reply.

We are using dust sensor. Sensor is having 2.5mm pitch 5 pin connector. The following is the way I connected the sensor to the BBB.

I connected power supply to the P9_05 header and Ground to P9_01 pin.

Sensor is sending PWM signal to BBB. so , I connected the output pin of the sensor to the P9_14(PWM pin) and use the python script (Adafruit Library) to read the PWM pin.

But I am getting the following error:

PWM.start("P9_14", 50, 1000)

Runtime Error: Unknown error

Can you please suggest me solution for this problem?

Note: We tried with all the PWM pins in BBB. But I received the same error.

Thanks & Regards,

Manimekala Rajendran.

0 Yordan Kovachev over 6 years ago in reply to Manimekala Rajendran

TI__Guru**** 161600 points

Hi,

Problem is that PWM pins are outputs. You can have a look at the ECAP module to see if it works for you. See Section 15.3 Enhanced Capture (eCAP) Module in AM3358 TRM. See the BBB schematics to see which expansion pins is possible to be muxed as ECAP in, refer to Table 4-1. Pin Attributes (ZCE and ZCZ Packages) in the Datasheet & Section 9.2.2 Pad Control Registers in the TRM.

Another option (that is if the pwm signal is not very fast) is to use GPIO pins as inputs.

Best Regards,
Yordan

0 Manimekala Rajendran over 6 years ago in reply to Yordan Kovachev

Intellectual 370 points

Hi,

I could not find section 15.3 in the link that you have mentioned.

Can you please send me the reference once again?

Thanks & Regards,

Manimekala Rajendran

0 Yordan Kovachev over 6 years ago in reply to Manimekala Rajendran

TI__Guru**** 161600 points

Here is the link to the TRM:
www.ti.com/.../spruh73p.pdf

Best Regards,
Yordan

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Linux/AM3358: PWM signal capture