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- # Protocols
-
- Some subsystems (and in the case of KEY and EMIT, the core) re-
- quire drivers to implement certain words in a certain way. For
- example, the core requires drivers to implement (key?) and
- (emit) or else it won't know how to provide a console.
-
- These protocols are described here.
-
- # TTY protocol
-
- (key?) -- c? f Returns whether a key has been pressed and,
- if it has, returns which key. When f is
- false, c is *not* placed in the stack.
- (emit) c -- Spit a character on the console.
-
- # PS/2 protocol
-
- This protocol enables communication with a device that spits
- PS/2 keycodes.
-
- (ps2kc) -- kc Returns the next typed PS/2 keycode from the
- console. 0 if nothing was typed.
-
- # SPI Relay protocol
-
- This protocol enables communication with a SPI relay. This
- protocol is designed to support devices with multiple endpoints.
- To that end, (spie) takes a device ID argument, with a meaning
- that is up to the device itself. To disable all devices, supply
- 0 to (spie).
-
- We expect relay devices to support only one enabled device at
- once. Enabling a specific device is expected to disable the
- previously enabled one.
-
- (spie) n -- Enable SPI device
- (spix) n -- n Perform SPI exchange (push a number, get a
- number back)
-
- # Grid protocol
-
- A grid is a device that shows as a grid of ASCII characters and
- allows random access to it.
-
- COLS -- n Number of columns in the device
- LINES -- n Number of lines in the device
- CELL! c pos -- Set character at pos
-
- Optional:
- NEWLN ln -- "Enter" line ln
- CURSOR! new old -- Move cursor from old pos to new pos
-
- "pos" is a simple number (y * cols) + x. For example, if we
- have 40 columns per line, the position (x, y) (12, 10) is 412.
-
- CELL! is not expected to be called with an out-of-range char-
- acter. For example, glyphs are often mapped starting at 0x20
- (space). On most systems, CELL! should not be called with c <
- 0x20.If it is, CELL! should do nothing.
-
- NEWLN is called when we "enter" a new line, that is, when we
- overflow from previous line or when 0x0d ( ASCII CR ) is emit-
- ted.
-
- When this is called, the line being entered should be cleared
- of its contents. On some systems, some kinf of screen offset
- might be have to be set to give a "scrolling" effect. Now's the
- time.
-
- If it's not defined, the grid system uses multiple CELL!
- calls to clear it. On some devices, this is highly inefficient.
- Drivers for those devices should define NEWLINE.
-
- CURSOR! is called whenever we change the cursor's position. If
- not implemented, it will be a noop. It is never called with an
- out of range "pos" (greater than COLS*LINES).
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