30d354c290
- Stop fighting against the SDK in terms of owning/writing the init_data block. NodeMCU included a default init_data block because originally the SDK did not, but by now it's not needed. - Expose a way to reconfigure the ADC mode from Lua land. With most people using the cloud builder and not able to change the #define for byte 107 this has been a pain point. - Less confusion about which init_data has been used. Lua code can now simply state what mode it wants the ADC to be in, and not worry about the rest of the init_data complexities such as the init_data changing location due to flashing with wrong flash_size setting, or doing/not doing a chip-erase before loading new NodeMCU firmware.
2.1 KiB
ADC Module
| Since | Origin / Contributor | Maintainer | Source |
|---|---|---|---|
| 2014-12-24 | Zeroday | jmattsson | adc.c |
The ADC module provides access to the in-built ADC.
On the ESP8266 there is only a single-channel, which is multiplexed with the battery voltage. Depending on the setting in the "esp init data" (byte 107) one can either use the ADC to read an external voltage, or to read the system voltage (vdd33), but not both.
Which mode to use the ADC in can be configured via the adc.force_init_mode() function. Note that after switching from one to the other a system restart is required before the change takes effect.
adc.force_init_mode()
Checks and if necessary reconfigures the ADC mode setting in the ESP init data block.
####Syntax
adc.force_init_mode(mode_value)
####Parameters
mode_value One of adc.INIT_ADC or adc.INIT_VDD33.
####Returns True if the function had to change the mode, false if the mode was already configured. On a true return the ESP needs to be restarted for the change to take effect.
####Example
-- in you init.lua:
if adc.force_init_mode(adc.INIT_VDD33)
then
node.restart()
return -- don't bother continuing, the restart is scheduled
end
print("System voltage (mV):", adc.readvdd33(0))
####See also
node.restart()
adc.read()
Samples the ADC.
####Syntax
adc.read(channel)
####Parameters
channel always 0 on the ESP8266
####Returns the sampled value (number)
If the ESP8266 has been configured to use the ADC for reading the system voltage, this function will always return 65535. This is a hardware and/or SDK limitation.
####Example
val = adc.read(0)
adc.readvdd33()
Reads the system voltage.
####Syntax
adc.readvdd33()
####Parameters none
####Returns system voltage in millivolts (number)
If the ESP8266 has been configured to use the ADC for sampling the external pin, this function will always return 65535. This is a hardware and/or SDK limitation.