Innotech SpitFIRE I, User Manual

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Spit FIRE Innotech Systems Inc. Page 7
PROGRAMMING INTERFACE DESCRIPTION
The Spit
FIRE
is controlled via a full-duplex bi-directional asynchronous
serial interface operating at 2400 baud, 8 data bits, with no parity. A host
CPU can manipulate the Spit
FIRE by writing commands in the form of
simulated button presses to it. The Spit FIRE will respond by returning
status information for every command.
To maintain flow control, the Spit FIRE will not return a status response
byte until it has processed the previous command.
The command byte consists of 7 scancode bits and one button-pressed bit.
Command byte to Spit FIRE
D7 D6 D5 D4 D3 D2 D1 D0
Button
pressed
Scan Code
This gives a maximum capacity of 128 buttons. The button pressed bit has
several purposes.
‚
It provides a way to hold down a button for an arbitrarily long
period of time.
‚
It provides a flow control mechanism between the two asynchron-
ous processors. Some commands are executed very quickly (10s of
microseconds) and some are quite slow (100s of milliseconds).
‚ It provides a way to distinguish two consecutive identical button
presses.
Commands are sent to the Spit FIRE in the form of “virtual” keypad
scancodes. The 7 LSBs of the command are the scancode. This gives the
system 128 virtual buttons that can be “pressed.” Of these 128 buttons the
Spit
FIRE
uses a subset to represent the buttons on a typical remote control.
After the Spit
FIRE
has received and acted on a command it will return a
status byte. The status byte tells the host processor how the previous
scancode was dealt with. It also tells the system that it can send another
command. The details of the status byte are covered later in this document.
The Spit FIRE can be configured to transmit IR messages indefinitely, or it
can be instructed to transmit an IR message a fixed number of times and
Spit FIRE Innotech Systems Inc. Page 8
then stop. When sending an indefinite length IR message, a ‘ transmitting IR
now’ status message is returned at the start of a transmission. Subsequently,
when a button release command is sent, the Spit FIRE completes the current
transmission and then it returns the appropriate status.
Special scancodes are available to tell the Spit FIRE to transmit IR message
until told to stop, or to send messages a fixed number of times. The auto-
repeat range is from 1 to 8 messages. A setting of 0 tells the Spit
FIRE
to
send the message continuously until the button is released.
When the transmit N times feature is used, the Spit
FIRE
will not return a
status byte until the IR transmission is completely sent (N times) so that the
system knows that the transmission is complete.
The following is a list of scancodes that a system can send to the Spit
FIRE
.
Codes are in hexadecimal and do not include the button-pressed bit.
Scan Codes
Code Code Function Notes
0 00h #0
1 01h #1
2 02h #2
3 03h #3
4 04h #4
5 05h #5
6 06h #6
7 07h #7
8 08h #8
9 09h #9
10 0Ah ENTER
11 0Bh MUTE
12 0Ch VOL+
13 0Dh VOL-
14 0Eh CH+
15 0Fh CH-
16 10h REWIND
17 11h PLAY
18 12h FF
19 13h RECORD
20 14h STOP
21 15h PAUSE