I was struggling to flash my device with openocd after I started using RTFM while googling I found this message:
https://www.jsykora.info/2014/10/error-jtag-status-contains-invalid-mode-value-communication-failure-solved/

adding this at the top of my init seems to have helped:

	#[init(schedule = [toggle])] 
	unsafe fn init() {
        let dbg = device.DBG;
        dbg.cr.modify(|_, w| w.dbg_sleep().set_bit());
    }