When I ordered my first Freedom FRDM-KL25Z board, I placed an order the Tower TWR-KL25Z48M shortly afterwards. But I was so happy with the FRDM-KL25Z, and because the FRDM board is much less expensive and easier to handle, that Tower board was sitting in my board shelf, waiting for a maybe a student project or to get any other use of it. Well, I can tell that my students wanted the FRDM board, not the Tower board ;-). But when I saw this week in the Freescale forum a user asking for a USB example for that Tower board, I thought that now I could at least use that board to help someone out.

MKL25Z128VLK4 on the TWR-KL25Z48M Board

The good news is that at least for the USB applications, my USB demo projects on GitHub for FRDM-KL25Z work 1-to-1 with the Tower board too. Yes, peripherals like LED’s are not on the same ports, but to quickly test the USB functionality, that Tower board should  work too.

So I downloaded my code from the FRDM-KL25Z, and then: nothing! No USB enumeration :-(.

Until I checked the schematics, and found that magical jumper J18 which needs to be enabled to power the USB block on the CPU. This is how the board ships with default jumpers:

TWR-KL25Z with Default Jumper Settings

To enable USB operation, jumper J18 needs to be enabled:

J18 Enabled on TWR-KL25Z to enable USB Operation

With this jumper set, the USB enumerated properly:

HID Keyboard Device from TWR-KL25Z

I only can speculate that this jumper is not set to save power on the CPU/board, but for out of the box experience I would have expected that USB would be enabled out of the box. But anyway, I have found it :-).

Happy Towering 🙂