ADC read wrong value

[TheB1ackSheep]

I just build firmware from http://nodemcu-build.com/ with adc module and it is always return 65535.

[Tertiush]

I'm having the same issue, tried both the master and dev branches and both read 65535, even if the pin is grounded.

It appears as if the current build only has the 3.3Vdd pin enabled for ADC function:

// Byte 107 of esp_init_data_default, only one of these 3 can be picked

define ESP_INIT_DATA_ENABLE_READVDD33

//#define ESP_INIT_DATA_ENABLE_READADC //#define ESP_INIT_DATA_FIXED_VDD33_VALUE 33

Not sure how to get a build where the ADc is mapped to TOUT.

[Tertiush]

There's something weird going on here....

When I use adc.readvdd33() then it appears to actually read the ADC pin, although the rails are incorrect. The range is from 26 to 4094, for a dead short and full 3.3V applied to pin (I realise 1V is the max.).

See if that also works for you?

[eyaleb]

This is not a bug, but a "feature" of the SDK, where it says to leave TOUT unconnected to read Vdd. However I do not know how to set the config to read TOUT in nodemcu-build.com.

If you build at home: to read TOUT with adc.read(0) you need to select it in app/include/user_config.h:

// Byte 107 of esp_init_data_default, only one of these 3 can be picked
//#define ESP_INIT_DATA_ENABLE_READVDD33
#define ESP_INIT_DATA_ENABLE_READADC
//#define ESP_INIT_DATA_FIXED_VDD33_VALUE 33

You will not be able to use adc.readvdd33().

[Tertiush]

Understood.

However reading the 3.3V supply actually gives me the TOUT value. In the printout below "Water_Sensor" is a normalised version of adc.readvdd33() and tracks the ADC (TOUT) pin correctly, not the supply rails:

Temperature: 24 deg C Humidity: 36% Water Sensor: 0% *Wifi status: 1 Temperature: 24 deg C Humidity: 36% Water Sensor: 28% *Wifi status: 1 Temperature: 24 deg C Humidity: 36% Water Sensor: 0%

[marcelstoer]

I do not know how to set the config to read TOUT in nodemcu-build.com.

It's not supported. You may want to try a custom build using the Docker image: https://github.com/marcelstoer/docker-nodemcu-build.

[fixingthingsguy]

My issue is similar but a bit confounding. I get different analog values with different hardware using a standard "frightanic dev or master build". NODEMCU dev board with AI thinker written on it - adc.read(0) works fine NODEMCU dev.board with nameless on board -adc.read(0) gives 65535 which is an error I believe. I want to use the same build, so its a bit of a problem if I have to use different builds to secure ADC(Tout). Not sure if there is a way out. I did try to make a custom build, but as, they say, "lord have mercy". Its not for everybody! I'm a novice kind of guy, no make/build knowledge , and the myriad steps, specifity of the recipe, etc, is such that to make a custom build is not for me, now. I just hope the community will come up with some creative way of not having to use custom builds for nuts and bolts operations, such as using an ADC. Is there a simple hardware fix that can work on the one board, and not on the other?

[mvilla14]

I have the same problem reading with the function ​​adc.read(0) always returns 65535 , I using the SDK 1.5.1 floating.bin ( created with cloud build service ) , but it also happens with SDK 0.9.6 floating.bin, strangely it was in operation properly with both SDK, but at a certain point began to fail and return 65535. What would be the solution ? . The adc.readvdd33 () function returns a value of approximately Vdd.

[jmattsson]

@mvilla14 Per the docs, use the Espressif flash download tool to write a different esp_init_data block to change the value of byte 107.

[mvilla14]

It solved perfectly , thanks.

2016-02-01 4:06 GMT-02:00 Johny Mattsson notifications@github.com:

@mvilla14 https://github.com/mvilla14 Per the docs https://nodemcu.readthedocs.org/en/dev/en/modules/adc/, use the Espressif flash download tool to write a different esp_init_data block to change the value of byte 107.

— Reply to this email directly or view it on GitHub https://github.com/nodemcu/nodemcu-firmware/issues/911#issuecomment-177786367 .

Ing. Mario Villa (0381) 4312487 (0381) 153441414

[TheB1ackSheep]

@mvilla14 How did you solve it?

[mvilla14]

I edit the 'Esp_init_data_default.bin' file, and at position 107, I put the value 33 which is corresponding to a supply voltage of 3.3V, thus reading is enabled 'adc.read(0)'.

2016-02-01 12:03 GMT-02:00 Falook Glico notifications@github.com:

@mvilla14 https://github.com/mvilla14 How did you solved it?

— Reply to this email directly or view it on GitHub https://github.com/nodemcu/nodemcu-firmware/issues/911#issuecomment-177984495 .

Ing. Mario Villa (0381) 4312487 (0381) 153441414

[n8twj]

Could someone explain the process of generating the Init Bin using Flash download tool? both settings i have tried adc.read(0) always returns 65535, but i am not sure I am doing it correctly.

$ python ./esptool.py --port=/dev/tty.wchusbserial1410 write_flash -fm=dio -fs=32m 0x7C000 ~/Development/esp/esp_init_data_default.bin Connecting... Erasing flash... Wrote 1024 bytes at 0x0007c000 in 0.1 seconds (68.7 kbit/s)...

Also, building via the Docker image, I have tried all three values (one at a time) in app/include/user_config.h and adc.read(0) always returns 65535 :(

$ python ./esptool.py --port=/dev/tty.wchusbserial1410 write_flash -fm=dio -fs=32m 0x00000 ~/Development/nodemcu-firmware/bin/nodemcu_float_master_20160201-2011.bin Connecting... Erasing flash... Wrote 477184 bytes at 0x00000000 in 56.8 seconds (67.2 kbit/s)...

Leaving...

from Esplorer: =adc.read(0) 65535

[devsaurus]

but i am not sure I am doing it correctly.

$ python ./esptool.py --port=/dev/tty.wchusbserial1410 write_flash -fm=dio -fs=32m 0x7C000

Correct location for the init data is 0x3fc000 on a 4 MByte flash: Chapter 3 in 2A_ESP8266_SDK Getting_Started_Guide_EN_v1.5_20151118.pdf

[n8twj]

This works... Thank you! I edited byte 107 (as documented) and wrote to nodemcu like this:

$ python ./esptool.py --port=/dev/tty.wchusbserial1410 write_flash -fm=dio -fs=32m 0x3fc000 ~/Downloads/esp_init_data_default.bin Connecting... Erasing flash... Wrote 1024 bytes at 0x003fc000 in 0.1 seconds (68.7 kbit/s)...

=adc.read(0) 181 <--- moisture sensor in wet soil =adc.read(0) 634 <--- moisture sensor pulled out (open air)

[fixingthingsguy]

Thank you community! This is a merciful way rather than doing a rebuild. An uber merciful way would be to get Expressif to change the default to ADC(Tout). It would distinguish their device from those that do not have ADC(Tout) and would enable a lot more people to use it.

[ybycode]

Thanks for this. For those who'd like to change the esp_init_data_default.bin file and can't use the Espressif flash download tool (which is for MS Windows only), here is the command line that does the work:

printf '\x21' | dd of=esp_init_data_default.bin bs=1 seek=107 count=1 conv=notrunc

It worked for me, I then flashed the file with the same command as @n8twj:

./esptool.py --port=/dev/ttyUSB0 write_flash -fm=dio -fs=32m 0x3fc000 esp_init_data_default.bin

[gkzsolt]

Thanks, ybycode, I have the same problems and tried this way. However, I get the following error on write_flash: `$ esptool.py --port=/dev/ttyUSB0 write_flash -fm=dio -fs=32m 0x3fc000 esp_init_data_default.bin Connecting... Erasing flash... Took 0.01s to erase flash block

A fatal error occurred: Failed to enter Flash download mode (result "0x1, 0x6")`

I got esp_init_data_default.bin from https://github.com/espressif/ESP8266_AT/tree/master/bin (one year old, is it good?). Also, I am trying to flash over the nodemcu build, if this is all right. No luck, however.

[gkzsolt]

Ok, solved, by getting the last firmware from Espressif. This post helped me navigate through the not-so-nice chinese site ;)

After writing 33 to address 107 adc.read(0) seems to work, although not quite in sync with my multimeter;) I wonder if anybody did an evaluation of their ADC?

[Wifsimster]

If someone has the nodemcu-build.bin with the correct fix, i'm looking for it.

Thanks.

[marcelstoer]

a) this is not a support forum -> http://nodemcu.readthedocs.io/en/latest/en/support/ b) ADC can be set in Lua at runtime -> http://nodemcu.readthedocs.io/en/latest/en/modules/adc/#adcforce_init_mode c) you need an up-to-date firmware (1.5.1) for that -> http://nodemcu.readthedocs.io/en/latest/en/build/