This is a carrier board for an Adafruit Feather device, designed specifically for the ESP32-S3 Feather. It breaks out two UARTs into IR transceivers, and SPI to a microSD slot.
There are three sets of components for the IR transceivers, but only two can be used. The sections marked IR1 are shared, connected to UART1, and only one section needs to be populated. The section marked IR2 is connected to UART2.
Technically, the only components that have to be installed are one transceiver and two links to power them (across R1/R3 on the top, R2/R4 on the left, and R6/R13 on the right). The capacitors improve stability but aren't strictly required. The other resistors are pull-ups for the SD lines (recommended but makes little practical difference) and pull-ups for the IR shutdown (only really necessary if you plan on shutting down the CPU)
IR1 is connected to UART1 on the standard Feather TX/RX pins, which are on GPIOs 39 and 38, respectively. IR2 is connected to UART2 on GPIOs 5 and 6. Each transceiver has an active low enable pin that is by default pulled high. These are on GPIOs 8 and 9 for IR1 and IR2.
Enabling IrDA mode requires setting UART_IRDA_EN in UART_CONF0_REG.
Additionally, to transmit, you need to set UART_IRDA_TX_EN. By
default, IrDA mode is half duplex, and UART_IRDA_TX_EN needs to be
toggled to switch between transmit and receive modes. To enable both
transmit and receive at the same time, which will echo all transmitted
data through the RX line, set UART_IRDA_DPLX.
For reasons I don't understand, the only thing that can be set via IDF
APIs is enabling IrDA mode. All of the other IrDA settings are not
available via IDF APIs, so you will likely have to twiddle the registers
directly. In C, this can be done by including soc/uart_struct.h and
using the bitfield structs provided. i.e.
UART1.conf0.irda_dplx = 1;
| GPIO Pin | Function |
|---|---|
| 39 | Transmit |
| 38 | Receive |
| 8 | Enable (active low) |
| GPIO Pin | Function |
|---|---|
| 5 | Transmit |
| 6 | Receive |
| 9 | Enable (active low) |
The SD card is connected to SPI such that it should be usable directly through the IOMUX on IOs 35, 36, and 37. CS is connected to GPIO 11. Card detect is connected to GPIO 13.
Additionally, DAT1 and DAT2 (only used in SD mode) are connected to GPIOs 12 and 10, respectively, so you should theoretically be able to enable 4-bit SD through the SD/MMC controller.
| GPIO Pin | Function |
|---|---|
| 36 | SCK |
| 35 | MOSI |
| 37 | MISO |
| 11 | CS |
| GPIO Pin | Function |
|---|---|
| 36 | CLK |
| 35 | CMD |
| 37 | DAT0 |
| 11 | CD |
| GPIO Pin | Function |
|---|---|
| 36 | CLK |
| 35 | CMD |
| 37 | DAT0 |
| 12 | DAT1 |
| 10 | DAT2 |
| 11 | DAT3 |
GPIOs 14-18 are unused and are broken out for futher expansion. The I2C lines are also available, as well as VBATT, VBUS, 3V3, GND, EN, and ~RST.
The board is 1.4 inches wide and 2.3 inches tall (35.56 x 58.42mm). The component sizes should be similar to their footprint outlines, giving it a maximum horizontal extent of 1.51" (38.354mm) with both side IR transceivers installed, and a maximum vertical extent of 2.51" (63.754mm) with the top transceiver installed and an SD card inserted.
Four mounting holes on the corners are sized for M2.5 screws. They are 0.11" (2.794mm) from the edges, which is also the corner radius.
A 0.15x0.25 inch (3.81x6.35mm) cutout is provided near the Feather's battery connector in the upper right. This allows any battery cables to be routed below the board even if the board is mounted flush against a case.