# Project Echo ## Description High-level modular schematic requirements for a Teensy 4.1 based RFID-triggered audio system with Bluetooth input, analog source selection, stereo amplification, and 12V to 5V power partitioning. ## Project Details - **Owner:** zekethoreson - **Created:** 4/7/2026 - **Last Updated:** 4/7/2026 - **Visibility:** Public - **Power Requirements:** 12V input rail feeds stereo amplifier directly and buck regulator input. Buck regulator creates 5V rail for controller-side power. Teensy 3V3 rail is distributed to RFID readers and SGTL5000 functional audio block. Common GND used across digital, analog, Bluetooth, and power blocks with star-ground intent. - **Connectivity:** Shared SPI bus from Teensy to four RFID readers using SPI_SCK, SPI_MOSI, SPI_MISO, and shared RFID_RST, with unique RFID1_SS through RFID4_SS chip selects. Audio sources BT_L/BT_R and CHAR_L/CHAR_R feed stereo switch controlled by AUDIO_MODE_SEL, then route as AMP_IN_L and AMP_IN_R to the amplifier. - **Design Notes:** Naming convention uses explicit rail and interface nets: 12V, 5V, 3V3, GND, SPI_SCK, SPI_MOSI, SPI_MISO, RFID_RST, RFID1_SS, RFID2_SS, RFID3_SS, RFID4_SS, AUDIO_MODE_SEL, BT_L, BT_R, CHAR_L, CHAR_R, AMP_IN_L, AMP_IN_R. TS3A5018 throw assignment and Bluetooth module supply rail remain flexible as long as source identity and rail partitioning remain explicit. - **Implementation Details:** High-level requirements-capture schematic only. Uses module-level or functional placeholder blocks to define power partitioning, shared SPI RFID architecture, analog audio source routing, and amplifier interfaces. Detailed passives, protection, decoupling, exact Audio Shield implementation, and final Bluetooth module supply selection are intentionally deferred. - **System Architecture:** ```mermaid flowchart TD subgraph PWR [Power] JIN[12V Input] BUCK[12V to 5V Buck] R12[12V Rail] R5[5V Rail] R33[3V3 Rail from Teensy] end subgraph CTRL [Controller] T41[Teensy 4.1] ASH[Teensy Audio Shield] end subgraph RFID [RFID Subsystem] R1[RFID Reader 1] R2[RFID Reader 2] R3[RFID Reader 3] R4[RFID Reader 4] end subgraph SRC [Audio Sources and Selection] BT[Bluetooth Stereo Receiver] SW[TS3A5018 Stereo Switch] end subgraph AMP [Amplifier and Output] PA[TPA3116D2 Stereo Amplifier] SPL[Left Speaker] SPR[Right Speaker] end JIN --> BUCK JIN --> R12 BUCK --> R5 T41 --> R33 R5 --> T41 R5 --> ASH R5 --> R1 R5 --> R2 R5 --> R3 R5 --> R4 R5 --> BT R12 --> PA T41 -->|I2S and control| ASH T41 -->|SPI SCK MOSI MISO RFID_RST RFID1_SS RFID2_SS RFID3_SS RFID4_SS| R1 T41 -->|Shared SPI| R2 T41 -->|Shared SPI| R3 T41 -->|Shared SPI| R4 BT -->|BT_L BT_R| SW ASH -->|CHAR_L CHAR_R| SW T41 -->|AUDIO_MODE_SEL| SW SW -->|AMP_IN_L AMP_IN_R| PA PA --> SPL PA --> SPR ``` ## Key Components ### Audio Shield — [SGTL5000XNLA3](https://www.flux.ai/vasyl/sgtl5000xnla3~gn4.md) - Manufacturer Part Number: SGTL5000XNLA3 - Role Details: Represents the Teensy Audio Shield Rev D functional interface for requirements capture. Used here as an SGTL5000-based placeholder because a usable schematic-level shield module is not available in the library. - Package: QFN-20 - Datasheet URL: https://www.nxp.com/docs/en/data-sheet/SGTL5000.pdf - Implementation Details: Functional placeholder for Teensy Audio Shield Rev D. Detailed shield implementation intentionally deferred. High-level interfaces captured as CHAR_L, CHAR_R, codec power at 3V3, and controller-facing digital audio/control links to be finalized in detailed design. - Manufacturer Name: NXP - Part Type: Integrated Circuit - Role: Audio Shield Functional Block **Pins:** - CTRL_CLK [pin 19] - CTRL_DATA [pin 18] - GND [pin 21] - HP_L [pin 4] - HP_R [pin 1] - HP_VGND [pin 2] - I2S_DIN [pin 17] - I2S_DOUT [pin 16] - I2S_LRCLK [pin 14] - I2S_SCLK [pin 15] - LINEIN_L [pin 9] - LINEIN_R [pin 8] - LINEOUT_L [pin 7] - LINEOUT_R [pin 6] - MIC [pin 10] - MIC_BIAS [pin 11] - SYS_MCLK [pin 13] - VAG [pin 5] - VDDA [pin 3] - VDDD [pin 20] - VDDIO [pin 12] ### Bluetooth Module — [TS3008](https://www.flux.ai/yevha/ts3008-xwhex~5o.md) - Manufacturer Name: Tinysine Electronics - Part Type: IC - Manufacturer Part Number: TS3008 - Package: Module - Role: Bluetooth Audio Receiver - Symbol Style: Parametric - Implementation Details: Bluetooth receiver treated as a module-level stereo analog source. BT_L and BT_R are routed to the source select switch. Module supply remains abstract pending final module choice; support either 5V or 12V powered receiver during detailed design. - Datasheet URL: https://cdn2.flux.ai/copilot-datasheets/pdf-upload-0d0e67742ccf5b24a430bcda1d7f3b5963d252f0bc72bfe570ec99b9fb1f3f6e/513c5fdc6839b385dc8a29b39c33e87ac15c1ab8571a5859de6c114df095768e.pdf?GoogleAccessId=graviton-mvp%40appspot.gserviceaccount.com&Expires=4881417022&Signature=WSsYFLpfkzgy5ZeNpDPfpt%2BeJMPtrNgsxT%2F%2F%2BiKUzLJGylw2%2BeYYqGKC%2BRjbDqFMTjGqapWGbdr5DSdNyQvz7FrybWXrjDr%2B5FOJ2FJGvTKmt8sypza%2FUEnQgZ9Hj%2BTQggYCzdJGAPFTL4NP2tNWSrrmDCmlu0iW3p%2FwM0%2B2a%2BIQ4OzgoViDbMc10OQe%2Bv%2B4cbVn0l%2BSze4Ug9%2BZjkAPcWq5jGvyrtFLPadCp1zS9nhIHKNTAh8v2Rjd3SvBB9kOsxGaW4ZfNjWBe7%2FGzKZwsRxID2L%2BacDQa%2Be1iBsLe2aNeJxJMHfxekkakbranjFjOWm12qPsO7tdMU6F1JpQOQ%3D%3D - Role Details: Line-level stereo Bluetooth receiver block feeding the analog source switch. Power input intentionally left abstract at this stage to support either 5V or 12V module variants during detailed design. **Pins:** - 1V8 [pin 10] - AIO0 [pin 6] - GND [pin 40] - GND [pin 26] - GND [pin 17] - LED0 [pin 28] - LED1 [pin 5] - LED2 [pin 29] - LINE_BN [pin 33] - LINE_BP [pin 32] - LINE/MIC_AN [pin 35] - LINE/MIC_AP [pin 34] - MIC BIAS [pin 31] - NC [pin 13] - NC [pin 12] - PIO0 [pin 4] - PIO1 [pin 3] - PIO16 [pin 11] - PIO17 [pin 7] - PIO18 [pin 15] - PIO21 [pin 14] - PIO6 [pin 1] - PIO7 [pin 9] - PIO8 [pin 2] - PIO9 [pin 8] - RSTn [pin 20] - SPI_CLK [pin 22] - SPI_CSB [pin 23] - SPI_MISO [pin 24] - SPI_MOSI [pin 21] - SPI_PCM# [pin 16] - SPK_AN [pin 38] - SPK_AP [pin 39] - SPK_BN [pin 36] - SPK_BP [pin 37] - USB_N [pin 19] - USB_P [pin 18] - VBAT [pin 27] - VCHG [pin 25] - VREG_EN [pin 30] ### Buck Regulator — [ST1S10PUR](https://www.flux.ai/kicad-part-library/st1s10pur~mx.md) - Package: DFN-8 - Package or Case Code: DFN-8-1EP_4x4mm_P0.8mm_EP2.5x3.6mm - Manufacturer Part Number: ST1S10PUR - Implementation Details: High-level buck regulator block converts 12V input rail to 5V rail for controller-side subsystems. Detailed passives, feedback network, and compensation intentionally deferred to detailed schematic design. - Role: Buck Regulator - Datasheet URL: http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00169322.pdf - Role Details: High-level 12V to 5V power conversion block supplying controller, audio logic, RFID readers, and Bluetooth module requirements. **Pins:** - AGND [pin 4] - FB [pin 3] - INH [pin 2] - PADGND [pin 9] - PGND [pin 8] - SW [pin 7] - SYNC [pin 5] - VINA [pin 1] - VINSW [pin 6] ### J1 — [Barrel Jack 373](https://www.flux.ai/adrian95/barrel-jack-373~0vr.md) - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: 373 - Implementation Details: Represents the main external 12V input connector. This stage captures the 12V rail entry point and common GND return only. - Manufacturer Name: Adafruit - Package: Connector - Datasheet URL: https://cdn-shop.adafruit.com/datasheets/21mmdcjackDatasheet.pdf - Role Details: Main 12V input entry point for the system power architecture. - Role: 12V Input Connector - Part Type: Connector **Pins:** - A [pin 1] - B [pin 2] - C [pin 3] ### J2 — [282837-4](https://www.flux.ai/adrian95/282837-4~o7p.md) - Part Type: Connector - Manufacturer Name: TE Connectivity AMP Connectors - Implementation Details: Represents speaker outputs from the stereo amplifier. Pin 1 SPK_L_P, pin 2 SPK_L_N, pin 3 SPK_R_P, pin 4 SPK_R_N. - Role Details: Four-position output connector carrying left and right speaker outputs from the stereo amplifier. - Datasheet URL: https://www.te.com/usa-en/product-282837-4.datasheet.pdf - Manufacturer Part Number: 282837-4 - Package: Terminal Block - License: https://creativecommons.org/licenses/by/4.0/ - Role: Speaker Output Connector **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] ### Main Controller — [Teensy 4.1](https://www.flux.ai/adrian95/teensy-4p1~xp5.md) - Datasheet URL: https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/2942/DEV-16996_Web.pdf - Role Details: Teensy 4.1 controller module. Hosts shared SPI for four RFID readers, drives audio source select control, provides 3V3 reference rail, and interfaces to the audio shield. - Role: Main Controller - Manufacturer Name: SparkFun Electronics - Implementation Details: Pin mapping reserved for requirements capture: SPI_SCK pin 13, SPI_MOSI pin 11, SPI_MISO pin 12, RFID_RST pin 6, RFID1_SS pin 10, RFID2_SS pin 9, RFID3_SS pin 8, RFID4_SS pin 7, AUDIO_MODE_SEL pin 32. Teensy 5V input from buck rail. Teensy 3V3 rail distributed to RFID readers and SGTL5000 functional block. - Manufacturer Part Number: DEV-16996 - Package: Module - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Development Board **Pins:** - 0_ [pin 2] - 1_ [pin 3] - 10_ [pin 12] - 11_ [pin 13] - 12_ [pin 14] - 13_ [pin 35] - 14_ [pin 36] - 15_ [pin 37] - 16_ [pin 38] - 17_ [pin 39] - 18_ [pin 40] - 19_ [pin 41] - 2_ [pin 4] - 20_ [pin 42] - 21_ [pin 43] - 22_ [pin 44] - 23_ [pin 45] - 24_ [pin 16] - 25_ [pin 17] - 26_ [pin 18] - 27_ [pin 19] - 28_ [pin 20] - 29_ [pin 21] - 3_ [pin 5] - 30_ [pin 22] - 31_ [pin 23] - 32_ [pin 24] - 33_ [pin 25] - 34_ [pin 26] - 35_ [pin 27] - 36_ [pin 28] - 37_ [pin 29] - 38_ [pin 30] - 39_ [pin 31] - 3V [pin 15] - 3V3 [pin 46] - 4_ [pin 6] - 40_ [pin 32] - 41_ [pin 33] - 5_ [pin 7] - 5V [pin 48] - 6_ [pin 8] - 7_ [pin 9] - 8_ [pin 10] - 9_ [pin 11] - G_1 [pin 1] - G_2 [pin 34] - G_3 [pin 47] ### RFID Reader — [RC522 RFID](https://www.flux.ai/jecstronic/rc522-rfid~dc6.md) - Part Type: Module - Role Details: RFID reader 1 using shared SPI bus with dedicated chip select RFID1_SS and shared reset RFID_RST. - Manufacturer Part Number: RC522 - License: https://creativecommons.org/licenses/by/4.0/ - Role: RFID Reader - Package: Module - Datasheet URL: http://www.handsontec.com/dataspecs/RC522.pdf - Manufacturer Name: Handson Technology **Pins:** - GND [pin 3] - IRQ [pin 4] - MISO/SCL/Tx [pin 5] - MOSI [pin 6] - RST [pin 2] - SCK [pin 7] - SS/SDA/Rx [pin 8] - VCC [pin 1] ### RFID Reader — [RC522 RFID](https://www.flux.ai/jecstronic/rc522-rfid~dc6.md) - License: https://creativecommons.org/licenses/by/4.0/ - Role: RFID Reader - Datasheet URL: http://www.handsontec.com/dataspecs/RC522.pdf - Manufacturer Name: Handson Technology - Package: Module - Part Type: Module - Manufacturer Part Number: RC522 - Role Details: RFID reader 3 using shared SPI bus with dedicated chip select RFID3_SS and shared reset RFID_RST. **Pins:** - GND [pin 3] - IRQ [pin 4] - MISO/SCL/Tx [pin 5] - MOSI [pin 6] - RST [pin 2] - SCK [pin 7] - SS/SDA/Rx [pin 8] - VCC [pin 1] ### RFID Reader — [RC522 RFID](https://www.flux.ai/jecstronic/rc522-rfid~dc6.md) - Manufacturer Part Number: RC522 - Part Type: Module - Role Details: RFID reader 4 using shared SPI bus with dedicated chip select RFID4_SS and shared reset RFID_RST. - Role: RFID Reader - Datasheet URL: http://www.handsontec.com/dataspecs/RC522.pdf - Manufacturer Name: Handson Technology - Package: Module - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - GND [pin 3] - IRQ [pin 4] - MISO/SCL/Tx [pin 5] - MOSI [pin 6] - RST [pin 2] - SCK [pin 7] - SS/SDA/Rx [pin 8] - VCC [pin 1] ### RFID Reader — [RC522 RFID](https://www.flux.ai/jecstronic/rc522-rfid~dc6.md) - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: RFID reader 2 using shared SPI bus with dedicated chip select RFID2_SS and shared reset RFID_RST. - Role: RFID Reader - Manufacturer Name: Handson Technology - Datasheet URL: http://www.handsontec.com/dataspecs/RC522.pdf - Part Type: Module - Manufacturer Part Number: RC522 - Package: Module **Pins:** - GND [pin 3] - IRQ [pin 4] - MISO/SCL/Tx [pin 5] - MOSI [pin 6] - RST [pin 2] - SCK [pin 7] - SS/SDA/Rx [pin 8] - VCC [pin 1] ### Stereo Amplifier — [TPA3116D2](https://www.flux.ai/jecstronic/tpa3116d2~2va.md) - Role: Stereo Amplifier - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: TPA3116D2 - Part Type: Integrated Circuit - Role Details: 12V powered TPA3116D2-based stereo amplifier block receiving line-level stereo input from the source selector and driving left and right speakers. - Manufacturer Name: Texas Instruments - Package: HTSSOP-32 - Datasheet URL: https://www.ti.com/lit/ds/symlink/tpa3116d2.pdf - Implementation Details: High-level stereo amplifier block powered from 12V rail. Inputs are AMP_IN_L and AMP_IN_R from source selector. Outputs are differential speaker pairs SPK_L_P, SPK_L_N, SPK_R_P, SPK_R_N to speaker terminal block. **Pins:** - AM0 [pin 15] - AM1 [pin 14] - AM2 [pin 13] - AVCC [pin 17] - BSNL [pin 20] - BSNR [pin 26] - BSPL [pin 24] - BSPR [pin 30] - FAULTZ [pin 3] - GAIN/SLV [pin 8] - GND [pin 9] - GND [pin 22] - GND [pin 28] - GND [pin 25] - GVDD [pin 7] - LINN [pin 11] - LINP [pin 10] - MODSEL [pin 1] - MUTE [pin 12] - OUTNL [pin 21] - OUTNR [pin 27] - OUTPL [pin 23] - OUTPR [pin 29] - PLIMIT [pin 6] - PVCC [pin 19] - PVCC [pin 32] - PVCC [pin 18] - PVCC [pin 31] - RINN [pin 5] - RINP [pin 4] - SDZ [pin 2] - SYNC [pin 16] ### Stereo Source Selector — [TS3A5018DBQR](https://www.flux.ai/jecstronic/ts3a5018dbqr~gsc.md) - Part Type: Integrated Circuit - Manufacturer Name: Texas Instruments - Role: Stereo Source Selector - Role Details: Dual SPDT analog switch selecting Bluetooth or Teensy audio shield stereo line source under AUDIO_MODE_SEL control. - Manufacturer Part Number: TS3A5018DBQR - Implementation Details: AUDIO_MODE_SEL selects stereo source. Design intent: LOW selects Bluetooth source, HIGH selects character audio source. Exact throw mapping may be finalized during detailed design as long as labeled nets preserve source identity. - License: https://creativecommons.org/licenses/by/4.0/ - Package: SSOP-16 - Datasheet URL: https://www.ti.com/lit/ds/symlink/ts3a5018.pdf **Pins:** - 1 [pin 1] - 10 [pin 10] - 11 [pin 11] - 12 [pin 12] - 13 [pin 13] - 14 [pin 14] - 15 [pin 15] - 16 [pin 16] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] - 5 [pin 5] - 6 [pin 6] - 7 [pin 7] - 8 [pin 8] - 9 [pin 9] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/zekethoreson/project-echo~sc](https://www.flux.ai/zekethoreson/project-echo~sc).* --- *Generated from [https://www.flux.ai/zekethoreson/project-echo~sc](https://www.flux.ai/zekethoreson/project-echo~sc)*