SPMA084 December   2021 TM4C1230C3PM , TM4C1230C3PM , TM4C1230D5PM , TM4C1230D5PM , TM4C1230E6PM , TM4C1230E6PM , TM4C1230H6PM , TM4C1230H6PM , TM4C1231C3PM , TM4C1231C3PM , TM4C1231D5PM , TM4C1231D5PM , TM4C1231D5PZ , TM4C1231D5PZ , TM4C1231E6PM , TM4C1231E6PM , TM4C1231E6PZ , TM4C1231E6PZ , TM4C1231H6PGE , TM4C1231H6PGE , TM4C1231H6PM , TM4C1231H6PM , TM4C1231H6PZ , TM4C1231H6PZ , TM4C1232C3PM , TM4C1232C3PM , TM4C1232D5PM , TM4C1232D5PM , TM4C1232E6PM , TM4C1232E6PM , TM4C1232H6PM , TM4C1232H6PM , TM4C1233C3PM , TM4C1233C3PM , TM4C1233D5PM , TM4C1233D5PM , TM4C1233D5PZ , TM4C1233D5PZ , TM4C1233E6PM , TM4C1233E6PM , TM4C1233E6PZ , TM4C1233E6PZ , TM4C1233H6PGE , TM4C1233H6PGE , TM4C1233H6PM , TM4C1233H6PM , TM4C1233H6PZ , TM4C1233H6PZ , TM4C1236D5PM , TM4C1236D5PM , TM4C1236E6PM , TM4C1236E6PM , TM4C1236H6PM , TM4C1236H6PM , TM4C1237D5PM , TM4C1237D5PM , TM4C1237D5PZ , TM4C1237D5PZ , TM4C1237E6PM , TM4C1237E6PM , TM4C1237E6PZ , TM4C1237E6PZ , TM4C1237H6PGE , TM4C1237H6PGE , TM4C1237H6PM , TM4C1237H6PM , TM4C1237H6PZ , TM4C1237H6PZ , TM4C123AE6PM , TM4C123AE6PM , TM4C123AH6PM , TM4C123AH6PM , TM4C123BE6PM , TM4C123BE6PM , TM4C123BE6PZ , TM4C123BE6PZ , TM4C123BH6PGE , TM4C123BH6PGE , TM4C123BH6PM , TM4C123BH6PM , TM4C123BH6PZ , TM4C123BH6PZ , TM4C123BH6ZRB , TM4C123BH6ZRB , TM4C123FE6PM , TM4C123FE6PM , TM4C123FH6PM , TM4C123FH6PM , TM4C123GE6PM , TM4C123GE6PM , TM4C123GE6PZ , TM4C123GE6PZ , TM4C123GH6PGE , TM4C123GH6PGE , TM4C123GH6PM , TM4C123GH6PM , TM4C123GH6PZ , TM4C123GH6PZ , TM4C123GH6ZRB , TM4C123GH6ZRB , TM4C1290NCPDT , TM4C1290NCPDT , TM4C1290NCZAD , TM4C1290NCZAD , TM4C1292NCPDT , TM4C1292NCPDT , TM4C1292NCZAD , TM4C1292NCZAD , TM4C1294KCPDT , TM4C1294KCPDT , TM4C1294NCPDT , TM4C1294NCPDT , TM4C1294NCZAD , TM4C1294NCZAD , TM4C1297NCZAD , TM4C1297NCZAD , TM4C1299KCZAD , TM4C1299KCZAD , TM4C1299NCZAD , TM4C1299NCZAD , TM4C129CNCPDT , TM4C129CNCPDT , TM4C129CNCZAD , TM4C129CNCZAD , TM4C129DNCPDT , TM4C129DNCPDT , TM4C129DNCZAD , TM4C129DNCZAD , TM4C129EKCPDT , TM4C129EKCPDT , TM4C129ENCPDT , TM4C129ENCPDT , TM4C129ENCZAD , TM4C129ENCZAD , TM4C129LNCZAD , TM4C129LNCZAD , TM4C129XKCZAD , TM4C129XKCZAD , TM4C129XNCZAD , TM4C129XNCZAD

 

  1.   Trademarks
  2. 1Introduction
  3. 2Pulse Width Modulation (PWM) emulation of a DAC
  4. 3Audio Sampling Rate and Resolution Analysis
    1. 3.1 Using the PWM DAC Method
    2. 3.2 Using Off-Chip DAC
  5. 4Audio File Data Format
    1. 4.1 WAV File Size Calculation
    2. 4.2 Storing WAV Audio on Internal Flash
  6. 5Hardware Setup
    1. 5.1 BOOSTXL-AUDIO BoosterPack Overview
    2. 5.2 Hardware Setup for EK-TM4C1294XL
    3. 5.3 Hardware Setup for EK-TM4C123GXL
    4. 5.4 Hardware Setup for DK-TM4C129x Development Board
  7. 6Application Examples
    1. 6.1 Examples: audio_playback_internal_wavefile_by_PWM_EKTM4C129 and audio_playback_internal_wavefile_by_SPIDAC_EKTM4C129
    2. 6.2 Examples: audio_playback_internal_wavefile_by_PWM_EKTM4C123 and audio_playback_internal_wavefile_by_SPIDAC_EKTM4C123
    3. 6.3 Examples: audio_playback_internal_wavefile_by_PWM and audio_playback_internal_wavefile_by_SPIDAC
    4. 6.4 Examples: audio_playback_with_sdcard_by_PWM and audio_playback_with_sdcard_by_SPIDAC
  8. 7Download and Import the Examples
  9. 8References

1 Introduction

Digital audio is a representation of sound recorded in digital form. In a digital audio system, an analog signal representing the sound can be converted, with an analog-to-digital converter (ADC), into a digital signal using the pulse code modulation (PCM) method. In PCM, the amplitude of an analog signal is sampled regularly at uniform intervals and each sample is quantized into digital steps. The uniform interval is called the sampling rate and the number of discrete levels a signal can be quantized into is called the bit depth. For example, CD audio achieves a sampling rate of 44.1 kHz with a bit depth of 16 bits. What this means is that an analog audio signal is sampled 44100 times in a second and the amplitude of the signal is quantized into 216 or 65536 steps.

Once the audio signal is digitized, it can be stored digitally as a file and it can be edited, modified, and manipulated using digital machines such as a computer or MCU. To play the digital audio file on a speaker, a reverse process is performed. The analog audio signal is simply recreated by using a digital-to-analog converter (DAC) to convert the digital signal back into an analog signal. The analog signal is then typically sent through an audio amplifier to boost the signal before reaching the speaker.

Figure 1-1 illustrates a generic digital audio synthesis and playback system. The DAC shown in the figure can be: an integrated component to the MCU, or a discrete component external to the MCU, or emulated by using PWM signal. As TM4C12x MCUs do not have an integrated DAC, this applicable report will demostrate playing back digital audio using both PWM emulation of a DAC and an external discrete DAC.

This application report focuses more on how the TM4C12x MCU can be used to playback rather than recording the digital music stored in an audio file.

GUID-20211108-SS0I-QC4H-NXX4-9H6B0FB4MQJ1-low.gifFigure 1-1 Example Audio Synthesis and Playback Systems