A-Tiny-20F
Amulet Baseboard 20F
The unique HVC Hybrid caps used for the 15F amulet base are going EOL as of 2025. While I can continue to make them based on exisiting stock, I designed a newer base board around the more common Lithium Ion Hybrid radial cylinder style capacitor. A compromise was made to keep the between board height the same by having a cut out for the cap. An additional 3d printed part to help protect and hold the cap is recommended as well.
Specifications
- MCU: ATTINY 1616
- Pins: Six pins for pwm, i2c, gpio
- Programming: WCH342F for UDPI over usb-uart programming and usb serial
- Charging: TI BQ25185 Charger
- Energy Storage: 4.0V 20F hybrid capacitor
- VDD: 1.8V to 3.6V, 1.8 to 5.0V configurable VDD
Pin Out
The A-TINY-20F is a drop in replacement for the A-TINY-15F, Only the charging and energy storage subsystem are different. The rest is the same.
| Pin | Port | PWM[^1] | Analog[^2] | PTC[^3] | Other |
|---|---|---|---|---|---|
| pin 1 | N/A | N/A | N/A | N/A | CFG1[^4] |
| pin 2 | N/A | N/A | N/A | N/A | CFG3[^4] |
| pin 3 | PA3 | WO_3 | AIN3 | NO | ExtCLK |
| pin 4 | GND | N/A | N/A | N/A | All Standoffs are GND |
| pin 5 | VDD | N/A | N/A | N/A | Voltage depends on R-CFG |
| pin 6 | PB0 | WO_0 | AIN11 | X5/Y5 | SCL |
| pin 7 | PA4 | WO_4 | AIN4 | X0/Y0 | |
| pin 8 | PB1 | WO_1 | AIN10 | X4/Y4 | SDA |
| pin 9 | PA5 | WO_5 | AIN5 | X1/Y1 | |
| pin 10 | PB2 | WO_2 | NO | NO |
Internal Pins: Pin PC0: Pin has been disconnected in this version of the board to keep safer. PIN PA7: Connected to VSEL of buck-boost. Pulling this pin high Selects Voltage 1, pulling this pin low selects Voltage 2.
Footnotes:
- 1: TCA0[^1]
- 2: ADC0[^2]
- 3: Peripheral touch controller[^3]
- 4: Connected to CFG1 and CFG3 on TPS63900 buck-boost regulator[^4]
MCU
same as the 15F version
Energy Storage
The energy storage is a 4.0V 20 farad Lithium ion hybrid capacitor. As per the data sheet and application notes I limit CC charging to ~80mA. Continuous current is rated for 80mA however for long running times I advise average currents to be kept low. I've had pwm animated leds run from 6-8 hours depending on average current draw. This cap is also socketed allowing for removal for maintainence or replacement.
Buck-Boost Converter
Same as the 15F version
Charging
Charging is done over USB connector. Same Type C connector. These use a TI CC/CV charging IC. This is meant for Li+ and LiFePo4 batteries but works for this hybrid cap. Charging voltage is set 4.05, discharge cutoff is set for 3.0v It is safe to discharge these caps to 2.5V but the IC ties it's cutoff with the charge voltage.
Versions/Changes
- 1.0 First version exists in prototypes
- Not released yet, some prototypes handed out
- 1.0 version considered functional but not as manufacturing friendly
Source Files
- codeberg source files
Misc
- Oshwa Certification (tbd)
- Amulet CrowdSupply Campaign
Datasheets
- Buck-Boost Converter TPS63900
- Charge Controller BQ25185
- MCU ATTINY1616
- Hybrid Capacitor Abracon AHCR Series Li+ Caps 20F