MarkEagle
VisorCentral Staff

Registered: Dec 1999
Location: Connecticut USA
Posts: 2682 |
Re: But only if the HotSync port device is a keyboard...
quote: Originally posted by MPM
I don't know if any of the other keyboards out there use their own driver or rely on the serial driver in the Palm OS.
As far as I know, all external keyboards use a keyboard driver. The Visor also uses the KBD line on the hotsync connector to determine that it is connected to one.
quote:
Keyboard Detect - KBD
This active-low pin is held low in order to indicate the presence of a keyboard or a serial cradle. While KBD* is held low, the handheld expects data to be sent on the RXD pin. Refer to the next section on keyboard support for information on the keyboard data packet structure supported by the handheld.
When this signal is asserted in Visor, a keyboard daemon is automatically launched to support keyboard input. The signal is detected when the handheld is placed in the cradle. If the handheld is reset while in the cradle, the daemon will not be re-launched. When Hotsync is asserted, this signal is also polled to determine which communications library should be used.
The use of KBD is also how the external keyboards get their power (through the TXD line):
quote:
Transmit Data/Power - TXD
TXD connects directly to the CPU�s UART. Note that TXD is TTL level, not RS-232 level. This signal is used for asynchronous serial communications between the handheld and a cradle or peripheral. TXD is an output from the handheld and an input to a cradle or peripheral. Internally, this pin is the output of the gate with the series resistor. This pin provides up to 3 mA maximum at 2.7 V when KBD* is asserted for low-power peripherals, such as keyboards. Short circuit current is 6mA minimum.
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