2 layers33 × 23.9 mm
ESPTiny1614
tomtor/ESPTiny
KiCad ATtiny84/x14/x02 (SMD) and ESP-01 (ESP 8266) PCB boards
24 parts4GPL-3.0
2 layers26.4 × 23.9 mm
ESPTiny402
tomtor/ESPTiny4KiCad ATtiny84/x14/x02 (SMD) and ESP-01 (ESP 8266) PCB boards
- Size
- 26.4 × 23.9 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 21
- Nets
- 16
- Pads
- 73
- Tracks, vias
- 304, 25
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 27 Jun 2021
- Updated
- 25 May 2025
Overview
ESPTiny402 is an open-source printed circuit board by tomtor, from the tomtor/ESPTiny repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 26.4 × 23.9 mm with 21 parts on 16 nets, routed with 304 tracks and 25 vias.
It is built around the ATTINY402-SSN and BAT54S. Its parts include 5 resistors, 3 ICs, 3 connectors, 2 capacitors and 2 diodes. It belongs with the ESP32, ESP8266 and AVR (ATmega, ATtiny) boards of this library.
Main components
2
ATTINY402-SSN
SOIC-8-40℃~+105℃ 1.8V~5.5V 10bit 128Byte 20MHz 256Byte 4KB 6 8 Bit AVR Built-in FLASH SOIC-8 Microcontrollers (MCU/MPU/SOC) ROHSMicrochip TechnologyMicrocontrollers (MCU/MPU/SOC)
BAT54S
SOT-231 Pair Series Connection 1V@100mA 200mA 2uA@25V 30V 600mA SOT-23 Schottky Diodes ROHSMDDSchottky Diodes
README
README.mdATtiny84/16x4/x02 and ESP-01 (ESP8266) KiCad PCB and example code
Usage
The main function of the ATtiny is acting as a battery friendly low power co-processor for the ESP. A bit like the ULP low power co-processor of the ESP32, except with a lot more IO functions and program memory.
ATtiny and ESP combined use 22uA in sleep mode or even less when the ESP is switched off by the ATtiny with CS.
Usable on breadboard (ATtiny84: 9 rows high, leaves 2 rows empty and ATtiny16x4: 8 rows high) OR stand alone.
3 PCB designs: ATtiny84 or ATtiny16x4 or ATtinyx02
All components / features are optional:
- ATtiny84 or ATtiny1604 / ATtiny1614 or ATtiny202 / ATtiny402
- ESP-01 (When not used the connections/space can be used for any other (I2C) device)
- LED with resistor
- MCP1700 low quiescent current regulator
- BAT85 diode for Solar Charging panel (see https://www.thethingsnetwork.org/labs/story/a-cheap-stm32-arduino-node/step/solar-power)
- Voltage divider for measuring battery voltage
- Decoupling capacitors
- I2C communication between ESP and ATtiny (with optional 4k7 pull-up)
- ATtiny can restart ESP by pulling ESP Reset low
Example code
The ATtiny wakes up the ESP every 10 minutes by pulling RST low and sends a counter and the supply voltage to it.
OTA for the ESP
OTA for ESP program updates is activated for 20s when the I2C communication fails. This can be triggered by resetting the ESP by pulling the RST line low. Because the ATtiny is most of the time sleeping the I2C communication will fail.
There is a small chance that the ATtiny will reset the ESP during upload when the 10 minute interval is completed. You can prevent this by pulling the ATtiny RST low when using OTA, or just upload again.
Schemas
https://github.com/tomtor/ESPTiny/raw/master/ESPTiny.pdf
https://github.com/tomtor/ESPTiny/raw/master/ESPTiny1614.pdf
https://github.com/tomtor/ESPTiny/raw/master/ESPTiny402.pdf
Credits
Parts
21| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 1M | Resistor_SMD:R_1206_3216Metric | R2, R3 |
| 2 | 1u | Capacitor_SMD:C_1206_3216Metric | C1, C2 |
| 2 | 4k7 | Resistor_SMD:R_1206_3216Metric | R4, R5 |
| 2 | Conn_01x10_Male | Connector_PinHeader_2.54mm:PinHeader_1x10_P2.54mm_Vertical | J1, J2 |
| 1 | 220 | Resistor_SMD:R_1206_3216Metric | R1 |
| 1 | ATtiny402-SS | Package_SO:SOIC-8_3.9x4.9mm_P1.27mm | U2 |
| 1 | BAT54S | Package_TO_SOT_SMD:SOT-23 | D2 |
| 1 | Conn_01x04_Male | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | J3 |
| 1 | ESP-01v090 | ESP8266:ESP-01 | U1 |
| 1 | LED | LED_SMD:LED_1206_3216Metric | D1 |
| 1 | MCP1700 | Package_TO_SOT_SMD:SOT-23 | U3 |
| 1 | SolderJumper_2 | Jumper:SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm | JP1 |
| 1 | SolderJumper_2_Open | Jumper:SolderJumper-2_P1.3mm_Open_Pad1.0x1.5mm | JP2 |
| 1 | SolderJumper_3_Bridged12 | Jumper:SolderJumper-3_P1.3mm_Bridged12_RoundedPad1.0x1.5mm_NumberLabels | JP3 |
The 18 most common of 21 parts.
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Questions
How big is the ESPTiny402 PCB?
It measures 26.4 × 23.9 mm and has 2 copper layers, 1.6 mm thick.
What parts does the ESPTiny402 use?
21 parts, built around the ATTINY402-SSN and BAT54S. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the ESPTiny402 KiCad files?
From the tomtor/ESPTiny repository on GitHub, at the commit this page was made from: the board is ESPTiny402.kicad_pcb and its schematic ESPTiny.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the ESPTiny402 design in my own project?
Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).