PROCESSOR-SDK-AM437X: TSC_ADC0_and_general_purpose ADC

Pravin Raut

Prodigy 10 points

Part Number: PROCESSOR-SDK-AM437X

Tool/software:

Hi Team,

We are currently utilizing the ADC0 section of the AM437X in our project.

From ADC0, we are using both the 4-wire Touch Screen Controller (TSC) and four general-purpose ADC channels.

We have two separate threads handling TSC and ADC readings. However, we’ve observed that when the TSC is being read continuously, the general-purpose ADC readings get blocked, causing the system to hang at that point.

Below is the relevant portion of our device tree configuration for TSC and ADC:

tsc {
ti,wires = <4>;
/* Datasheet says resistance is between 450 and 1200 ohm. */
ti,x-plate-resistance = <825>;
ti,coordinate-readouts = <5>;
ti,wire-config = <0x00 0x11 0x22 0x33>;
ti,charge-delay = <0xB000>;
};

adc {
ti,adc-channels = <4 5 6 7>;
};

Could you please suggest a way to manage ADC access so that general-purpose ADC readings are not blocked during TSC operations?

Thanks
Pravin Raut

7 months ago

0 Karam Haddad 7 months ago

TI__Intellectual 1090 points

Hi Pravin,

Please allow me some time to look into this and I will get back to you with an update by Wednesday 9/10.

Regards,
Karam

0 Karam Haddad 7 months ago in reply to Karam Haddad

TI__Intellectual 1090 points

Hi Pravin,

I forwarded this to the team and I'm waiting to hear back from them. I'll let you know as soon as I have an update.

Regards,
Karam

0 Karam Haddad 7 months ago

TI__Intellectual 1090 points

Hi Pravin,

It looks like the root cause is that the TSC is running in Continuous Mode, which keeps the shared ADC sequencer busy and prevents your GP-ADC steps from running. As the AM437x TRM Section 11.3.4 One Shot (Single) or Continuous Mode states, "If continuous mode is selected, it is the software’s responsibility to turn off the step enable bit."

Given this, it's recommended not to run in continuous mode, and interleave the TSC and GP-ADC operations together through software.

Could you please further elaborate what you mean by "causing the system to hang at that point," and what software are you using to run this?

Regards,
Karam

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PROCESSOR-SDK-AM437X: TSC_ADC0_and_general_purpose ADC