ESP8266-HDK-dat.md
chip info
module HDK == ESP-12F-DAT
common pins
| pin | name | GPIO | function | Note | note |
|---|---|---|---|---|---|
| 25 | U0_RXD | 3 | IO3 | I/O UART Rx during flash programming | |
| 26 | U0_TXD | 1 | IO1 | SPI_CS1 | I/O UART TX during flash programming; |
| 14 | IO2 | 2 | U1_TXD | Flash debug output | |
| 13 | MTDO | 15 | U0_RTS | HSPI_CS | |
| 18~23 | SDIO | ||||
| 8 | XPD_DCDC | IO16 | Deep-sleep wakeup (need to be connected to EXT_RSTB); GPIO16 |
bootstrap
| pin | default boot | Against Mode | ESP-12F-dat | ESP-12S-dat | func |
|---|---|---|---|---|---|
| RESET | pull up + cap 0.1 UF | Reboot | ext. | int. | |
| EN | pull up | Reboot | ext. | int. | |
| IO0 | pull up | Flash Mode | ext. | int. | Boot mode control |
| IO2 | pull up | pull-up w/LED | pull-up w/LED | on-module LED | |
| GPIO15 | pull down | Fail into SDIO Mode | ext. | int. | MTDO |
- reference from chip datasheet section "Pin Definitions" Note part
Baud rate 74880 is what the ESP8266 bootloader uses. The apps on top of the Espressif SDK (e.g. Arduino sketch) talk at 115200 if not specified otherwise.
the normal reset boot
ets Jan 8 2013,rst cause:2, boot mode:(3,6)
load 0x40100000, len 28740, room 16
tail 4
chksum 0xef
load 0x33333333, len 858993459, room 4
the prog mode boot
ets Jan 8 2013,rst cause:2, boot mode:(1,7)
ADC
(4. Peripheral Interface)
Hardware Design - The input voltage range is 0 to 1.0 V when TOUT is connected to external circuit.
Schematic
The ESP8266EX schematics include seven aspects:
• Power supply • Power-on sequence and reset • Flash • Crystal oscillator • RF • External resistor • UART
GPIO 16
❌ What GPIO16 Cannot Do
| Feature | Support | Notes |
|---|---|---|
| PWM (analogWrite) | ❌ No | GPIO16 does not support hardware PWM. |
| Interrupts (attachInterrupt) | ❌ No | Cannot be used for interrupts. |
| I²C / SPI / UART | ❌ No | Not multiplexed for any peripheral functions. |
| Analog input | ❌ No | ESP8266 has only one ADC (ADC0), not on GPIO16. |
| Open-drain / Pull-up/down | ❌ No | Limited internal resistor configuration. |
| Output during deep sleep | ⚠️ Caution | When used for deep sleep wake, it must not be driven externally. |
✅ What GPIO16 Can Do
| Feature | Support | Notes |
|---|---|---|
| Digital output | ✅ Yes | Use with digitalWrite(). |
| Digital input | ✅ Yes | Use with digitalRead(). |
| Deep sleep wake | ✅ Yes | Connect GPIO16 to RST to enable timed wake from deep sleep. |
interrrupt
✅ Recommended GPIOs for Interrupts
| GPIO | Usable for Interrupts? | Notes |
|---|---|---|
| GPIO0 | ✅ Yes | Must be HIGH at boot (pulled LOW enters flash mode) |
| GPIO2 | ✅ Yes | Must be HIGH at boot |
| GPIO4 | ✅ Yes | Safe |
| GPIO5 | ✅ Yes | Safe |
| GPIO12 | ✅ Yes | Safe |
| GPIO13 | ✅ Yes | Safe |
| GPIO14 | ✅ Yes | Safe |