2023-09-29 initial commit
2023-09-30 fixed pinout to correspond to Xiao, added jumper to choose between RX/CS on pin 8, completely rerouted
| ⚡ The hardware design is tested and confirmed working as of the latest commit. Nevertheless I cannot guarantee anything. Use at your own risk! |
|---|
MIAO is a cheap drop-in replacement for the Seeeduino Xiao series.
喵 is the Hanzi for "miāo", which is Mandarin for "meow".
The board is available in two variants:
- A super cheap, hand-solderable version in
hw_handsolder(since castellated holes are expensive, this version doesn't support them.) - A cheap, pcba version in
hw_pcba, featuring castellated holes
Renders of the handsolderable version and a screenshot of the schematic can be unfolded below.
Front view render
Back view render
Schematic
MIAO features:
- Utilizes wch's ch552t microcontroller, which at the time of writing costs a few dozen cents!
- SPI and UART pins in the same places as Xiao (use jumper to choose between RX/CS on pin 8)
- 2 Analogue pins
- 4 additional broken out pins (not pads!) compared to the Xiao boards:
- 2 free GPIOs
- reset pin (pull HIGH for reset)
- boot pin (pull HIGH for entering bootloader)
- Full ESD protection incl. protection against reverse current and overcurrent
- Top-mount USB port for maximum drop-in-ability
- Optional power or user led (on the backside for the handsolderable version; bridge left and middle part of jumper for always-on, middle and right for user controllable via P3.3)
- Optional reset and bootloader buttons (on the backside for the handsolderable version)
- Optional footprint for connecting USB Shield to GND in a way that fits your application
- Cute pixel cat on the back! 🐱
As production files are open sourced, you can get these manufactured at your favorite PCB-manufacturer. Alternatively, keeb.supply is selling the PCBA version usage-ready for a great price! Thanks guys! <3 Non-affiliate link: Miao page on keeb.supply
This BOM is for the handsolderable version only. For the PCBA version please refer to the given files.
| Amount | Part | LCSC part number | Silkscreen Reference | Comment |
|---|---|---|---|---|
| 1 | ch552t microcontroller | C111367 | U1 | |
| 1 | top-mount USB-C receptacle | C2765186 | [none] | |
| 1 | SOT-23 ESD protection diode | C6807798 | U2 | |
| 1 | SOD-323 Schottky diode | C193668 | D2 | |
| 1 | 0603 Fuse | C311055 | F1 | |
| 1 | 0603 10kΩ Resistor | C25804 | R1 | |
| 2 | 0603 5.1kΩ Resistor | C23186 | R4, R5 | |
| 2 | 0603 100nF Capacitors | C384773 | C1, C2 | Take care, these need to be soldered in vertically, as indicated by the small dashes on the silkscreen! |
| [1] | [optional] 1kΩ Resistor | C21190 | R2 | on the backside |
| [2] | [optional] push buttons | C115357 | B, R | on the backside |
| [1] | [optional] LED | C434442 | D1 | on the backside |
The project is inspired by and designed for usage with semickolon's FAK firmware, but it's obviously not limited to that! Refer to the ch552t documentation and the many other ch55x projects for more details.
The hardware design is licensed under the CERN-OHL-v2-S license, so feel free to look at the sources and remix to your heart's content! :)
- semickolon for creating FAK, inspiring the project and helping with design considerations
- 0xCB for open-sourcing the Helios and providing inspiration for the ESD stuff
- the Clacktales community for their continued support, discussion, and interest in the project
- Pete Johanson for noticing and pointing out the pinout mix-up in the initially commited version