PlatformIO and WiFi credentials

1

I am still very new to vscode+PlatformIO but was interested in what I found in the documentation under platformio.ini. In the example that is provided is shows this:

build_flags =
    ${env.build_flags}
    -DSSID_NAME=HELLO
    -DSSID_PASWORD=WORLD

I am assuming that this sets the WiFi credentials. My question is, how do I used these in my script? At the moment I have something like:

const char* essid = "**********";
const char* psks = "***************";

Is these some global variable pair that I need to pick up in my code? Otherwise, how do I connect to my WiFi router? I was hoping to find something in the documentation, perhaps in the build options where the options are located in the example, but so far have not found any info.

BTW, I also recently came across WiFi Manager, a WiFi configuration manager library for Arduino. I haven’t investigated it yet, but wondering whether I actually need it in the vscode+PlatformIO environment?

2

The -D<macro name>=<value> option is an instruction to the compiler to create a macro with the given name and value. So, -DVAL=123 is the same as writing on top of every file

#define VAL 123

The documentation shows a further example of this. Important is the need to escape values / stringify them, just writing e.g. -DSSID_NAME=HELLO does create

#define SSID_NAME HELLO

and not:

#define SSID_NAME "HELLO"

Since it creates a regular macro, you can either refer to the macro directly, or use it to initialize a variable. Doesn’t make a lot of difference.

So, you could have

build_flags =
   '-DSSID_NAME="My Test"'
   '-DSSID_PASSWORD="Test Password"'

and use it as

#include <Arduino.h>
const char* essid = SSID_NAME;
const char* psks = SSID_PASSWORD;

void setup(){ Serial.begin(9600); }
void loop() { Serial.println(psks); }
3

Thank you. I did wonder whether that might be creating macros but wasn’t sure. That clarifies things a lot. Its certainly seems a better approach than hard-coding credentials in the code.

I have also today come across an example where someone is doing this:

[wifi]
ssid = mySSID
password = myPassword

Does this also create macros?

4

Writing that in platformio.ini itself does not do anything that affects the build. There would have to be an extra_script that transports these values into the build system, e.g. as a macro, such as shown here and here. However, for a simple macro addition, that is quite overkill…

5

Sorry, my bad! I missed in that same example where he had this in the build_flags which were right near the bottom of the rather long config :

'-DWIFI_SSID=${wifi.ssid}'
'-DWIFI_PASS=${wifi.password}'

So I see now that he is actually assigning the items configured earlier as section parameters to macros in the build flags. The extra script examples you posted are interesting as well. I see that this arrangement quite flexible.

6

Ah right, so extra scripts are indeed not the only way, since you can reference the value of other environments and variables, you can inject them into the build using build_flags again with ${env_name.variable name}, as documented. Thought only of the more complicated way here.

7

Indeed, as documented in the platformio.ini example, although without an explanation in the document text, I didn’t initially appreciate what the ${…} constructs were doing. My understanding is gradually improving and I appreciate your help.