Using Ethernet.begin(mac, ip) if/when Ethernet.begin(mac) fails

Projects Programming
1

Hello all-

I am writing a sketch where I want my micro to connect via DHCP, with a fallback option of using a programmed IP if not connected to DHCP.

I wrote the following:

if (!m_Settings.UseDHCP || (m_Settings.UseDHCP && !Ethernet.begin(mac)))
{
Ethernet.begin(mac, m_Settings.ip);
}

The problem is that when DHCP is not working and my code enters the if statement (which it will, after a few seconds, verified) the Ethernet.begin(mac, ip) won't work for some reason.

Any insight?

2

The problem is that when DHCP is not working and my code enters the if statement (which it will, after a few seconds, verified) the Ethernet.begin(mac, ip) won't work for some reason.

What do you mean by "enters the if statement"? An if statement doesn't have an entry point.

An if statement is evaluated. The result is either true or false. If true, the body of the if statement is executed.

So, just what DOES happen?

And, how do you KNOW?

3

I guess I meant enter the body of the if statement. I know I entered it because I printed in it like so and saw the output:

if (!m_Settings.UseDHCP || (m_Settings.UseDHCP && !Ethernet.begin(mac)))
{
Ethernet.begin(mac, m_Settings.ip);
Serial.println("Test");
}

As to what happens in this if statement, m_Setting.UseDHCP is a bool in a struct. When true, I want to try Ethernet.begin(mac). If m_Setting.UseDHCP == false, or if m_Setting.UseDHCP == true and Ethernet.begin(mac) returns 0, I want to execute Ethernet.begin(mac, ip).

4

You test the return code from the begin() method that uses DHCP, but not the one that doesn't. Is there a reason that you assume that the second method will always work?

What, exactly, IS the problem?