02. Requirements Defininition¶
This page is still a Work in progress.
PCB Design¶
PCB 1. to power the Rack¶
1. Microcontroller
For the brain of my board, the Microcontroller, after considering Xiao ESP32 (too few pins), ESP32-C6 (too complex for a beginner), I narrowed down to Pi Pico W (suggested by my instructor Nagano san) and the new Xiao Plus (suggested by Rico) which seem to satisfy all my requirements (Wi-fi, many programmable GPIOs, compatible with Arduino IDE, low price).
So I did a spec comparison:
| Microcontroller | Raspberry Pi Pico W | Xiao ESP32S3 Plus |
|---|---|---|
| MPU | Dual-core 32 bit cortex M0+, 133MHz | Dual-core 32-bit Xtensa LX7, 240MHz |
| Memory (ROM/SRAM/Flash) | 512kB/264kB/2MB | 384kB/8MB/16MB |
| GPIO | 26 | 18 |
| Other Interface | 2×UART, 2×I2C, 2×SPI, 3×12-bit ADC, 16×controllable PWM channels | 2x UART, 1x IIC, 1x IIS, 2x SPI, 18x GPIOs (PWM), 9x ADC, 1x User LED, 1x Charge LED, 1x B2B Connector, 1x Reset button, 1x Boot button |
| Power | USB port (5V) or VSYS pin (1.8 V-5.5 V), connected to power source such as battery. This input voltage is then converted to a suitable 3.3 V by an onboard voltage regulator. | Input voltage (Type-C): 5V, Input voltage (BAT): 4.2V, incl. Integrated Li-ion charging |
| Energy consumption in deep sleep mode | 1-2mA (1000-2000µA) | 14μA |
| Wi-Fi | Wi-Fi 4 2.4GHz/5.0GHz | 2.4GHz |
| Bluetooth | BLE 5.2 | BLE 5.0 |
| Not included | DAC, Touch Sensors | DAC, Touch sensors |
| Dimensions | 51mm x 21mm x 1mm Single board | 21 x 17.8mm |
| Language | C/C++, MicroPython, Lua, Arduino, Thonny | Arduino / MicroPython / ESP-IDF |
| Price | ￥1,200 | ￥1,203 |
(There also seems to be a new Pi Pico 2 W which unfortunately is not on sale in Japan yet.)
I liked the Xiao ESP32S3 Plus for the battery charging capability, low energy consumption, and high performance. But looking at the Pin-out Diagram revealed a unique footprint that make PCB designing a little too complex for this week’s assignment. Besides, the footprint data was not yet available. So I eventually settled on Xiao ESP32C3 for the purpose of this week’s task.
These are the Features and Pin out Diagram of Xiao ESP32C3:
These are the specs for the Xiao ESP32C3;
| Microcontroller | Xiao ESP32C3 (Datasheet) |
|---|---|
| MPU | Single-core 32 bit RISC-V, @160MHz |
| Memory (ROM/SRAM/Flash) | 384kB/400kB/4MB onboard Flash |
| GPIO | 11 digital I/O, 3 Analog I/O that can be used as ADC pins |
| Other Interfaces | 1xI2C, 1xSPI, 2xUART, 11xGPIO(PWM), 4xADC, 1xJTAG bonding pad interface |
| Power Pins | 5V out from the USB port (Can also use this as a voltage input but you must have some sort of diode b/2 external power source and this pin with anode to battery, cathode to 5V pin.) / 3V3 (the regulated output from the onboard regulator. Can draw 700mA) / GND |
| Battery charging pad | Supports lithium battery charge and discharge management |
| Built-in Button & LED | Reset Button, Bootloader Button, Charge LED |
| Energy consumption in deep sleep mode | 43μA |
| Wi-Fi | Complies with IEEE 802.11b/g/n protocol and supports Station mode, SoftAP mode, SoftAP + Station mode, and promiscuous mode. Includes external antenna to increase the signal strength. |
| Bluetooth | BLE 5.0 & Bluetooth Mesh |
| Not included | DAC, Touch Sensors |
| Dimensions | 21x17.8mm Single board |
| Language | Arduino / MicroPython |
| Price | $4.99 |
2. Analog Input
I need the rack to identify different bottle placements.
To enable my mini Xiao board (which only has 3 Analog I/O pins) to do this, I will use a Multiplexer (or 2) to achieve up to 32 Input I/Os.
1. LED output
I will need the same number of LEDs (and Resistors) as the Input I/Os I decide to implement.
Nagano-san also suggested using a Neo-Pixel type LED, so I am also planning to look into that.
4. Communication
For communication with the microphone device, I will consider some kind of wireless communication.
I need to research whether the Bluetooth and Wi-fi can both be used at the same time on the Xiao board.
For communication with additional boards (to achieve scalability), I concluded that I probably won’t be needing it after all, but these seem to be the common approaches;
- SPI (Serial Peripheral Interface): High-speed, full-duplex communication with a master-slave relationship, good for transferring large data blocks.
- I2C (Inter-Integrated Circuit): Multi-master capable, efficient for smaller data transfers between multiple devices on a bus.
- UART (Universal Asynchronous Receiver Transmitter): Simple, flexible protocol for basic text-based communication.
5. Power
I will need to do a Power Budgeting to decide in between using a Rechargeable battery or a Power outlet.
I will also need to figure out how I can enable the circuit to switch to Deep sleep mode.
To achieve scalability, I will use the 5V or 3V3 power pin to potentially relay the power to other boards.
Power Pins on the Xiao board;
- 5V - The 5v out from the USB port. Can also use this as a voltage input but you must have some sort of diode (schottky, signal, power) between my external power source and this pin with anode to battery, cathode to 5V pin.
- 3V3 - The regulated output from the onboard regulator. I can draw 700mA
- 1 GND - Power/data/signal ground
6. Debugging features
I will add a Power LED, Test LED and Test Button.
Design Planning¶
Use 8-ch Multiplexer to increase available GPIO pins Separate pins into Analog, Digial, and PWM. Analog and Digital better to not place next to each other One debugging LED and one button is enough
Breakout special pins for I2C communication, Recommended to have many ground pin and 5V pin connections