One thing you may want to try is to switch the TX and RX. It’s often confusing whether the TX pin on the serial converter should be connected to the TXD or RXD on the microcontroller.
I have not had any experience using Max232. I’ve been using the PL2383 USB-to-serial converter for debugging with OpenSprinkler and it works pretty well. We have this in store: http://rayshobby.net/cart/usb-pl2303
To use it you just need to plug in the ground (black) wire to OS ground, and the RX (white) wire to OS TXD pin. Then use a serial monitor (either Arduino’s serial monitor, or putty, or gtkterms etc.) to receive messages. The only downside with pl2303 is that on Windows you need to install driver.
I tried swapping RXD and TXD but it doesn’t work either. Is the programming side of things ok with my serial.begin() and println() statements? If so then I need to look at my HW again.
Update: I got it working. The issue was with the MAX232 driver chip, the supply voltage was just a bit too low for it to work properly. I will get myself a lower voltage version to try out. If all this works then I will move to Isolated RS485 so I can move OS to a remote location.
Can’t wait for Ray to enable the SD card and serve the content locally. This will remove the Internet dependency completely.