AM2434: Sinus Cosing resolver with AM243 ADC

Jan Bock

Intellectual 2750 points

Part Number: AM2434
Other Parts Discussed in Thread: ADS9234R, ADS7253, ADS7251

Tool/software:

A question about the ADC of the
AM243x:

We would like to use a SinCos resolver.

We assume: MaxRPM= 9000Rpm -> 150 revolutions / s

Number of lines of the
resolver = 120 lines.

This results in
18000 sin-periods / s = 55.5us per sin-period

We would like to use the both channels of the SinCos resolver SIMULTAN.
According to the data sheet of the AM243x, sampling with the ADC is NOT SIMULTANEOUS but only sequential.
How can we sample the two sin and cos values of the resolver into the processor without sampling delay in order to avoid angular displacements?

thanks

Jan

6 months ago

0 Swargam Anil 6 months ago

TI__Mastermind 34620 points

Hello Jan,

I have assigned this thread to an Hw expert to provide inputs on this requirement, and I am also notified in this thread. If there are any software related queries I will provide a reply.

Regards,

Anil.

+1 Kallikuppa Sreenivasa 6 months ago in reply to Swargam Anil

TI__Guru**** 159839 points

Hello Jan,

Refer below block in the TRM

Figure 12-6. Functional Block Diagram

Jan Bock said:
According to the data sheet of the AM243x, sampling with the ADC is NOT SIMULTANEOUS but only sequential.
How can we sample the two sin and cos values of the resolver into the processor without sampling delay in order to avoid angular displacements?

As you mentioned the ADC is sequential.

You may have to consider an ADC that samples simultaneously to the Sine

Please check if this helps

https://www.ti.com/tool/TIDA-00178

https://www.ti.com/tool/TIDA-00176

https://www.ti.com/tool/TIDA-01527

Regards,

Sreenivasa

0 Kallikuppa Sreenivasa 6 months ago in reply to Kallikuppa Sreenivasa

TI__Guru**** 159839 points

Hello Jan,

Please refer additional input i added based on my discussion with the device expert:

The ADC implemented in AM243x is a single channel SAR ADC with a multi-input analog multiplexer inserted on the input path. Therefore, it is not possible for the ADC to sample two inputs simultaneously.

Regards,

Sreenivasa

0 Jan Bock 6 months ago in reply to Kallikuppa Sreenivasa

TI__Intellectual 2750 points

Hello Kallikuppa,

yes this has been already clear to the customer. And if we understood correctly also an external ADC like ADS9234R does not work on the QSPI interface (maybe you can confirm that finally). So the only option would be either ADS9234R via PRU (this is not possible here because the PRU will be in use) or the decision that the customer made to use an ADS7253 or ADS7251.

Thank you

Jan

0 Kallikuppa Sreenivasa 6 months ago in reply to Jan Bock

TI__Guru**** 159839 points

Hello Jan,

Here is the list of ADCs that have been interfaced,

Jan Bock said:
And if we understood correctly also an external ADC like ADS9234R does not work on the QSPI interface (maybe you can confirm that finally). So the only option would be either ADS9234R via PRU (this is not possible here because the PRU will be in use)

QSPI i am not sure. PRU - understand.

Jan Bock said:
ADS7253 or ADS7251

refer section Terminal Descriptions of ADC data sheet. Any thoughts how customer plans to interface to Am243x?

Regards,

Sreenivasa

0 Jan Bock 6 months ago in reply to Kallikuppa Sreenivasa

TI__Intellectual 2750 points

Hello Kallikuppa,

Kallikuppa Sreenivasa said:
QSPI i am not sure

The documentation of the AM243 says that QSPI is only for memory interface. ADS9234R has a dual SDO line, so there for normal SPI does not work.

Kallikuppa Sreenivasa said:
refer section Terminal Descriptions of ADC data sheet. Any thoughts how customer plans to interface to Am243x?

For me it looks like through standard spi interface. Do you have any concerns here?

Thanks

Jan

0 Kallikuppa Sreenivasa 6 months ago in reply to Jan Bock

TI__Guru**** 159839 points

Hello Jan,

Thank you.

Jan Bock said:
Kallikuppa Sreenivasa said:
refer section Terminal Descriptions of ADC data sheet. Any thoughts how customer plans to interface to Am243x?

For me it looks like through standard spi interface. Do you have any concerns here?

As i understand, these ADCs also seem to have dual SDO output.

Regards,

Sreenivasa

0 Jan Bock 6 months ago in reply to Kallikuppa Sreenivasa

TI__Intellectual 2750 points

Hello Kallikuppa,

Kallikuppa Sreenivasa said:
As i understand, these ADCs also seem to have dual SDO output.

The ADS7253 has a Single-SDO mode:

whereas ADS9234R has not such a mode.

Regards

Jan

0 Kallikuppa Sreenivasa 6 months ago in reply to Jan Bock

TI__Guru**** 159839 points

Hello Jan,

Thank you for the inputs.

Regards,

Sreenivasa

0 Jan Bock 6 months ago in reply to Kallikuppa Sreenivasa

TI__Intellectual 2750 points

Hello Kallikuppa,

can you also clarify the contraints of the QSPI interface and why it is just declared as an memory interface?

Thanks

Jan

0 Kallikuppa Sreenivasa 6 months ago in reply to Jan Bock

TI__Guru**** 159839 points

Hello Jan,

Thank you.

TIs current implementations and software enablement has been around the OSPI/QSPI memory.

Regards,

Sreenivasa

0 Jan Bock 5 months ago in reply to Kallikuppa Sreenivasa

TI__Intellectual 2750 points

Kallikuppa Sreenivasa said:
TIs current implementations and software enablement has been around the OSPI/QSPI memory.

So this means that it is a software and not a hardware constraint, correct?

0 Kallikuppa Sreenivasa 5 months ago in reply to Jan Bock

TI__Guru**** 159839 points

Hello Jan,

Thank you.

Jan Bock said:
TIs current implementations and software enablement has been around the OSPI/QSPI memory.

So this means that it is a software and not a hardware constraint, correct?

I do not have a way to confirm the query.

This may require a detailed analysis.

Regards,

Sreenivasa

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AM2434: Sinus Cosing resolver with AM243 ADC