Difference between revisions of "Teensy 4.1 Computer"
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* Separate 5v and 3.3v supplies for audio circutry |
* Separate 5v and 3.3v supplies for audio circutry |
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* Barrel jack and screw terminal connections for VIN |
* Barrel jack and screw terminal connections for VIN |
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| + | == The Audio Circuit == |
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| + | [[File:Teensy41_Computer_Audio_circuit.png|thumb|Teensy 4.1 Computer audio circuit]] |
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| + | The Teensy 4.1 is connected to the audio circuit via the Teensy's I2S 2 port. This connection goes to the PCM5102 ADC. As is recommended in the PCM5102's datasheet, filtering is added to the output, however the filter used on this board is a bit stronger, using a 4.7nF capacitor instead of the 2.2nF capacitor recommended in the datasheet. The filter cutoff is still far above human perception, at 72kHz, and should filter high frequency noise a bit better. The connection to the OPA1688 is DC, not AC, coupled, but this is according to the recommendations in the OPA1688 datasheet. The gain of the amplifier is configured to be 1, so the output voltage of the amp should match the ADC's output voltage, and be in the range of 0v to 3.3v. A voltage divider is used to activate the PCM5102's soft mute function when the 5v line drops, whic is designed to prevent any pops in the audio when the power is disconnected. |
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Revision as of 16:50, 12 June 2024
The Teensy 4.1 Computer is more or less described by its name: Its a carrier board for the Teensy 4.1 which provides four USB ports, an Ethernet port, Hi-Fi audio, and several convenient expansion ports.
Detailed Specifications
USB:
- TUSB2046 USB Hub, providing 4 USB A ports
- Each port has a maximum of 1.5A output - the port will shutdown due to overcurrent above this
- Board power provides a maximum of 2A to the 5v supply
- one should be aware of this when considering the power used by USB devices
Audio:
- I2S control connected to Teensy I2S 2
- PCM5102 ADC for providing stereo sound
- OPA1688 for the amplifier
- 3.5mm audio jack, maximum 75mA per channel
- Separate ground, connected to main ground through a ferrite bead
- Separate 3.3v and 5v supplies from linear regulators to reduce noise
- Note: 5v line will come from main 5v rail if only powered from USB
Power:
- 2A 5v buck regulator (Exact part is the VR20S05)
- PMOS switches to prevent regulator backfeeding from USB and to control power flow (U16, U17, and U18 on the PCB)
- External VIN accepted from 8v to 20v
- Separate 5v and 3.3v supplies for audio circutry
- Barrel jack and screw terminal connections for VIN
The Audio Circuit
The Teensy 4.1 is connected to the audio circuit via the Teensy's I2S 2 port. This connection goes to the PCM5102 ADC. As is recommended in the PCM5102's datasheet, filtering is added to the output, however the filter used on this board is a bit stronger, using a 4.7nF capacitor instead of the 2.2nF capacitor recommended in the datasheet. The filter cutoff is still far above human perception, at 72kHz, and should filter high frequency noise a bit better. The connection to the OPA1688 is DC, not AC, coupled, but this is according to the recommendations in the OPA1688 datasheet. The gain of the amplifier is configured to be 1, so the output voltage of the amp should match the ADC's output voltage, and be in the range of 0v to 3.3v. A voltage divider is used to activate the PCM5102's soft mute function when the 5v line drops, whic is designed to prevent any pops in the audio when the power is disconnected.