Data Sheet

ESP8266 Datasheet
Espressif Systems
Espressif Systems
June1,2015
22
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32
The function used to test the input voltage of TOUT is: uint16 system_adc_read(void)
RF-init parameter in the following passage refers to esp_init_data_default.bin
Application One:
Test the power supply voltage of VDD3P3 (Pin 3 and Pin 4).
Hardware Design:
TOUT must be dangled.
RF-init Parameter: The 107th byte of
esp_init_data_default.bin
(0 - 127 byte),
“vdd33_const“, must set to be 0xFF, i.e., the value of “vdd33_const“ is 255.
RF Calibration
Process:
Optimize the RF circuit conditions based on the testing results of VDD3P3 (Pin 3
and Pin 4).
User Programming:
Use system_get_vdd33 instead of system_adc_read.
Application Two: Test the input voltage of TOUT (Pin6).
Hardware Design:
The input voltage range is 0 to 1.0 V when TOUT is connected to external
circuit.
RF-init Parameter: The value of the 107th byte of esp_init_data_default.bin (0 - 127
byte), “vdd33_const“, must be set to be the real power supply voltage of Pin
3 and Pin 4.
The working power voltage range of ESP8266EX 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 to36.
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 One:
In
RF_init
parameter
esp_init_data_default.bin
(0 - 127 byte), the 107th byte is defined as
“vdd33_const“. Definitions of “vdd33_const“ is described below:
（1） If vdd33_const = 0xff, the power voltage of Pin 3 and Pin 4 will be tested by the internal self-
calibration process of ESP8266EX chipset itself. RF circuit conditions should be optimized according
to the testing results.