TM4C129XKCZAD: Sample code of ADC

Danilo A.

Part Number: TM4C129XKCZAD
Other Parts Discussed in Thread: EK-TM4C1294XL

Hi Team,

Our customer is new to programming and would like to know how to set the ADC of TM4C129XKCZAD for 4 MHz sampling rate. I have checked our resource explorer and it seems we don't have sample code of ADC for TM4C129XKCZAD. According to our customer, he wants to get 1024 samples and print them on display (simple oscilloscope). He also wants to know if it is possible to measure negative voltage?

Regards,

Danilo

over 3 years ago

0 Ralph Jacobi over 3 years ago

TI__Guru*** 135355 points

Hello Danilo,

TM4C129XKCZAD code will be the same as anything for TM4C129x, they all have the same ADC module. There ADC examples we have include the adc_udma_pingpong example for the EK-TM4C1294XL LaunchPad which is a new example added in TivaWare 2.2.0 (this is not on Resource Explorer, it must be downloaded from TI.com) and our generic ADC examples located at [Install Path]\TivaWare_C_Series-2.2.0.295\examples\peripherals\adc

If 4 MHz sampling rate means 4 million samples per second as a rate, then that is a challenge. TM4C129x is limited to 2 million samples per second. However, one customer posted a way to get effectively 4 million samples per seconds by using both ADC modules. Perhaps this could help your customer: https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/699971/ccs-ek-tm4c1294xl-adc-with-dma-ping-pong-mem_buffer_size-limited-to-8/2580498#2580498

This thread is also insightful about how to maximize the ADC sample rate: https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/690227/ccs-ek-tm4c1294xl-adc-not-running-at-2msps-capped-at-1msps/2545036#2545036

Danilo A. said:
He also wants to know if it is possible to measure negative voltage?

A DC offset is required for any negative voltages to ensure the input into the MCU pins is above GND. The MCU will not accept negative voltages and the absolute minimum before potential IC damage is -0.3V. If a DC offset is used, then the ADC can be operated in Differential mode in order to handle the measurement, but the effective input range is then limited to +1.65V to -1.65V unless a voltage divider is used as well.

Best Regards,

Ralph Jacobi

0 Danilo A. over 3 years ago in reply to Ralph Jacobi

TI__Mastermind 28590 points

Hi Ralph,

Thank you for your response. We just received this feedback from our customer,

I can't find adc_udma_pingpong example results. Have got any documentation or tutorials how to display information from UART0, connected to the Virtual Serial Port and running at 115,200, 8-N-1, which is used to display messages from this application. How do I get this message?

Regards,

Danilo

0 Ralph Jacobi over 3 years ago in reply to Danilo A.

TI__Guru*** 135355 points

Hello Danilo,

Danilo A. said:
I can't find adc_udma_pingpong example results.

It will be at [Install Path]\TivaWare_C_Series-2.2.0.295\examples\boards\ek-tm4c1294xl\adc_udma_pingpong

If they do not have TivaWare 2.2.0 then they need to download it. We have better ADC collateral on 2.2.0 as part of improvements.

Danilo A. said:
Have got any documentation or tutorials how to display information from UART0, connected to the Virtual Serial Port and running at 115,200, 8-N-1, which is used to display messages from this application.

I don't know if we really have 'documentation' but this is done on many TivaWare examples. The simplest example is the hello project located at: [Install Path]\TivaWare_C_Series-2.2.0.295\examples\boards\ek-tm4c1294xl\hello

What documentation we have would be more on what each API does and how to use it.

Best Regards,

Ralph Jacobi

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TM4C129XKCZAD: Sample code of ADC