Datasheet

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4. Peripheral Interface
4.10. LED Light and Button
ESP8285 features 17 GPIOs, all of which can be assigned to support various functions of
LED lights and buttons. Definitions of some GPIOs that are assigned with certain functions
in demo application design are shown as below.
Altogether three interfaces have been defined, one is for the button, while the other two are
for LED light. Generally, MTCK is used to control the reset button, GPIO0 is used as a
signal to indicate the Wi-Fi working state, MTDI is used as a signal light to indicate
communication status between the device and the server.
RF Initialization Parameter
The value of the 107th byte of esp_init_data_default.bin (0 ~ 127 bytes),
vdd33_const must be set to the real power supply voltage of Pin 3 and Pin 4.
The working power voltage range of ESP8285 is between 1.8V and 3.6V, while
the unit of vdd33_const is 0.1V, therefore, the effective value range of
vdd33_const is 18 to 36.
RF Calibration Process
Optimize the RF circuit conditions based on the value of vdd33_const. The
permissible error is ±0.2V.
User Programming
Use system_adc_read󰲧instead of system_get_vdd33.
📖 Note:
esp_init_data_default.bin is provided in SDK package which contains RF initialization parameters (0 ~ 127
bytes).
You can define the 107th byte in esp_init_data_default.bin to vdd33_const as below.
• If vdd33_const = 0xff, the power voltage of Pin 3 and Pin 4 will be tested by the internal self-calibration
process of ESP8285 itself. RF circuit conditions should be optimized according to the testing results.
•
If 18 =< vdd33_const =< 36, ESP8285 RF Calibration and optimization process is implemented via
(vdd33_const/10).
• If vdd33_const < 18 or 36 < vdd33_const < 255, ESP8285 RF Calibration and optimization process is
implemented via the default value 2.5V.
Table 4-10. Pin Definition of LED and Button
Pin Name
Pin Num
IO
Function Name
MTCK
12
IO13
Button (Reset)
GPIO0
15
IO0
Wi-Fi Light
MTDI
10
IO12
Link Light
📖 Note:
Most interfaces described in this chapter can be multiplexed. Pin definitions that can be defined is not limited
to the ones herein mentioned, you can customize the functions of the pins according to your specific
application scenarios via software programming and hardware design.
Espressif
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2017.05