Comtrol eCos - Manual (Page 704)

Control Endpoints
...
const usbs_enumeration_data* enumeration_data;
void (*start_fn)(usbs_control_endpoint*);
...
};
It is the responsibility of higher-level code, usually the application, to define the USB enumeration data. This
needs to be installed in the control endpoint data structure early on during system startup, before the USB device
is actually started and any interaction with the host is possible. Details of the enumeration data are supplied in
the section
USB Enumeration Data . Typically, the enumeration data is constant for a given peripheral, although it
can be constructed dynamically if necessary. However, the enumeration data cannot change while the peripheral is
connected to a host: the peripheral cannot easily claim to be a keyboard one second and a printer the next.
The start_fn member is normally accessed via the utility usbs_start rather than directly. It is provided by the
device driver and should be invoked once the system is fully initialized and interaction with the host is possible.
A typical implementation would change the USB data pins from tristated to active. If the peripheral is already
plugged into a host then the latter should detect this change and start interacting with the peripheral, including
requesting the enumeration data.
State
There are three usbs_control_endpoint fields related to the current state of a USB slave device, plus some state
constants and an enumeration of the possible state changes:
typedef struct usbs_control_endpoint {
...
int state;
void (*state_change_fn)(struct usbs_control_endpoint*, void*,
usbs_state_change, int);
void* state_change_data;
...
};
#define USBS_STATE_DETACHED 0x01
#define USBS_STATE_ATTACHED 0x02
#define USBS_STATE_POWERED 0x03
#define USBS_STATE_DEFAULT 0x04
#define USBS_STATE_ADDRESSED 0x05
#define USBS_STATE_CONFIGURED 0x06
#define USBS_STATE_MASK 0x7F
#define USBS_STATE_SUSPENDED (1 << 7)
typedef enum {
USBS_STATE_CHANGE_DETACHED = 1,
USBS_STATE_CHANGE_ATTACHED = 2,
USBS_STATE_CHANGE_POWERED = 3,
USBS_STATE_CHANGE_RESET = 4,
USBS_STATE_CHANGE_ADDRESSED = 5,
USBS_STATE_CHANGE_CONFIGURED = 6,
USBS_STATE_CHANGE_DECONFIGURED = 7,
USBS_STATE_CHANGE_SUSPENDED = 8,
USBS_STATE_CHANGE_RESUMED = 9
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