Hello, I'm trying to connect up a bare metal version of the M0 mbed and load a simple program onto it via the USB bootloader. I'm having some problems...

I'm using the 64-pin version. I have connected the ISP (pin 5) and RESET (pin 4)lines via switches to ground (with pull-ups), and the USB_CON (pin 29) to a P-channel MOSFET as per Chris' design. I also have USB_VBUS (pin 19) pulled up to 3V3.

My PC recognises a USB device but it doesn't come up as a MSD device and I can't open the folder or find it in device manager.

Can someone walk me through exactly what needs to be pulled where and pressed when to invoke the USB bootloader and get it to appear as a drive on my PC?

0. apply 3,3V to the LPC11U24 1. Connect USB cable to your host PC. 2. have ISP# Low. 3. Take RESET# low, release it. 4. GNU/Linux (or if you must! Windows) should straightaway detect the removable drive.

Essential Check: the 12MHz crystal must be fitted. check it has no shorts, especially to V+ or GND

Thanks for the replies guys, one thing I'm using a 10MHz xtal (didn't have a 12MHz one). I thought taht this would just make the MCU run a bit slower but now beginning to think this may be the problem?

I don't have a schematic at the minute as I'm hacking this on a prototyping board but the design is as Chris' design here with the exception that the resistors and caps on the USB side of things are the right way round!

Martin

Bugger - got one on order should be coming in tomorrow...

I'm guess this is because of the USB clock frequencies??? Please explain for the unenlightened!

USB timings are fixed - and the code must derive them from a known source.

12MHz crystal is indispensible, really.

it is possible to program without crystal, if you use serial.

I have posted some detailed instructions, but cannot manage to find them using ny phone

Ceri

the new xtal done the trick - all up and running. Surprisingly easy to program it in this way, I'm impressed!

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