Hello,
I'd like to introduce a Teensy 4 PCM5242 Audio Shield.
It's part of a larger project to create a digital mixer based on the Teensy 4. I've experimented with a few different designs, but this one seems to make the most sense. It's a low-cost, high-performance DAC module for the Teensy 4 that features both Balanced and Single Ended output. It is long, thin, and designed to be stacked. This, and other similar audio modules (ADC, etc) can also be combined to create just the right combination of inputs and outputs for the intended use. The stack can be placed inside a project box on its side to save space and still fit inside a 1U enclosure. I'm also hoping that by stacking the boards, the I2S lines will stay short enough to work in multiples. I have created some prototypes of similar models, but this particular model hasn't yet been created. I'm interested in any feedback before I build it. Please feel free to comment. Thanks!
Key Features
• Small PCB - The Shield is 62mm by 22.5mm (2.44” by .89”)
• Stereo DAC with a high theoretical performance as specified in the PCM5242 datasheet.
o SNR 114dB
o Dynamic Range 114dB
o THD+N at - 1dBFS –94dB
o Full Scale Differential Output 4.2VRMS (GND center, 2.1VRMS per channel)
• Stereo Balanced Output (+4 dBu professional)
• Stereo Padded Single Ended Output (-10dBV consumer)
• Outputs via header pins (no audio jacks or connectors on board).
o Output 2 +
o Output 2 –
o Output 1 +
o Output 1 –
o Padded Output 1 +
o Padded Output 2 +
o Ground
• Stackable Design. The stackable design and jumper options will allow multiple units to be used simultaneously.
• Selectable Data Pins - The Teensy has 2 SAI sets, one with 2 serial data lines, and one with 5 serial data lines. Not all the exposed jumpers will work, because I believe 2 of the serial data pins are input only. I left them in there because I had the space. The other data lines are either intended by PJRC to be outputs, or are switchable between inputs and outputs (software support pending). Therefore, exposing jumpers for these data lines should make prototyping numerous boards together easier. A configuration of this board may be either multiple data lines via regular I2S or it can use TDM to have multiple units on the same line (4 units per data pin, 8 channels of audio). The jumper pads are a “hand solderable” 0603 pad for a 0 Ohm resistor.
• Selectable Master Clock Pins - The Teensy has 2 master clocks. There are two jumper pads which can be used to select which master clock is used. This is only experimental.
• Selectable I2C Pins - The Teensy 4 has 2 sets of I2C pins, and the board allows selecting use of either set. This may come in handy when having more than 4 of these boards stacked (The PCM5242 has up to 4 addresses on one I2C bus). (experimental).
• Selectable Address Jumpers - For changing between the 4 available addresses.
Board Schematic and BOM
View attachment TEENSY_4.0_PCM5242_AUDIO_SHIELD_v0.5.pdf
IO Board - XLR + RCA
And finally, there is a corresponding IO board for the audio output jacks.
Any Feedback?
I'd like to introduce a Teensy 4 PCM5242 Audio Shield.
It's part of a larger project to create a digital mixer based on the Teensy 4. I've experimented with a few different designs, but this one seems to make the most sense. It's a low-cost, high-performance DAC module for the Teensy 4 that features both Balanced and Single Ended output. It is long, thin, and designed to be stacked. This, and other similar audio modules (ADC, etc) can also be combined to create just the right combination of inputs and outputs for the intended use. The stack can be placed inside a project box on its side to save space and still fit inside a 1U enclosure. I'm also hoping that by stacking the boards, the I2S lines will stay short enough to work in multiples. I have created some prototypes of similar models, but this particular model hasn't yet been created. I'm interested in any feedback before I build it. Please feel free to comment. Thanks!
Key Features
• Small PCB - The Shield is 62mm by 22.5mm (2.44” by .89”)
• Stereo DAC with a high theoretical performance as specified in the PCM5242 datasheet.
o SNR 114dB
o Dynamic Range 114dB
o THD+N at - 1dBFS –94dB
o Full Scale Differential Output 4.2VRMS (GND center, 2.1VRMS per channel)
• Stereo Balanced Output (+4 dBu professional)
• Stereo Padded Single Ended Output (-10dBV consumer)
• Outputs via header pins (no audio jacks or connectors on board).
o Output 2 +
o Output 2 –
o Output 1 +
o Output 1 –
o Padded Output 1 +
o Padded Output 2 +
o Ground
• Stackable Design. The stackable design and jumper options will allow multiple units to be used simultaneously.
• Selectable Data Pins - The Teensy has 2 SAI sets, one with 2 serial data lines, and one with 5 serial data lines. Not all the exposed jumpers will work, because I believe 2 of the serial data pins are input only. I left them in there because I had the space. The other data lines are either intended by PJRC to be outputs, or are switchable between inputs and outputs (software support pending). Therefore, exposing jumpers for these data lines should make prototyping numerous boards together easier. A configuration of this board may be either multiple data lines via regular I2S or it can use TDM to have multiple units on the same line (4 units per data pin, 8 channels of audio). The jumper pads are a “hand solderable” 0603 pad for a 0 Ohm resistor.
• Selectable Master Clock Pins - The Teensy has 2 master clocks. There are two jumper pads which can be used to select which master clock is used. This is only experimental.
• Selectable I2C Pins - The Teensy 4 has 2 sets of I2C pins, and the board allows selecting use of either set. This may come in handy when having more than 4 of these boards stacked (The PCM5242 has up to 4 addresses on one I2C bus). (experimental).
• Selectable Address Jumpers - For changing between the 4 available addresses.
Board Schematic and BOM
View attachment TEENSY_4.0_PCM5242_AUDIO_SHIELD_v0.5.pdf
IO Board - XLR + RCA
And finally, there is a corresponding IO board for the audio output jacks.
Any Feedback?