212 lines
5.4 KiB
Text
212 lines
5.4 KiB
Text
== Serial (Optional Add-On)
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Declared in `<joey/serial.h>`.
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[IMPORTANT]
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====
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This header is *not* pulled in by `<joey/joey.h>`. Include it explicitly:
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[source,c]
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----
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#include <joey/joey.h>
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#include <joey/serial.h>
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----
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A program that never references `jlSerial*` pays nothing -- the linker drops
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the module entirely.
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====
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One byte-stream API spans every port while the HAL hides very different
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hardware: the IIgs drives a Zilog 8530 SCC directly or a 6551 card in a slot;
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DOS uses an interrupt-driven 8250/16550 UART; the Amiga uses `serial.device`;
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the ST goes through the BIOS Aux channel.
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The model is *non-blocking and buffered*. Received bytes accumulate in a
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background ring -- a hardware interrupt on DOS, the OS on Amiga and ST, or
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`jlSerialPoll` on the IIgs -- and reads never block. Call `jlSerialPoll` once
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per frame: it is a no-op where the interrupt or OS already fills the ring, and
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the hardware drain where it does not, so calling it every frame is always
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correct.
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A failed `jlSerialOpen` is non-fatal: it returns `false` and every other call
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becomes a safe no-op, exactly like a failed audio init.
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=== Types
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[source,c]
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----
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typedef enum {
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JL_SERIAL_DEFAULT = 0, // the platform's natural RS-232 port
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JL_SERIAL_MODEM, // IIgs modem port (SCC channel A)
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JL_SERIAL_PRINTER, // IIgs printer port (SCC channel B)
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JL_SERIAL_SLOT // card/port selected by config->unit
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} jlSerialDeviceE;
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typedef enum {
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JL_SERIAL_PARITY_NONE = 0, JL_SERIAL_PARITY_ODD, JL_SERIAL_PARITY_EVEN
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} jlSerialParityE;
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typedef enum {
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JL_SERIAL_FLOW_NONE = 0, // no handshaking
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JL_SERIAL_FLOW_RTSCTS, // hardware RTS/CTS
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JL_SERIAL_FLOW_XONXOFF // software XON/XOFF
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} jlSerialFlowE;
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typedef struct {
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uint32_t baud; // 300 .. 115200, clamped per port
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uint8_t dataBits; // 5 .. 8
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uint8_t stopBits; // 1 or 2
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jlSerialParityE parity;
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jlSerialFlowE flow;
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uint8_t unit; // JL_SERIAL_SLOT only
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} jlSerialConfigT;
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----
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The IIgs is the machine with three device choices; elsewhere `JL_SERIAL_MODEM`
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and `JL_SERIAL_PRINTER` both mean the default port. `JL_SERIAL_DEFAULT` selects
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the IIgs modem port, DOS COM1, the ST Modem port or Amiga unit 0.
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`unit` disambiguates `JL_SERIAL_SLOT` and is ignored otherwise: an IIgs Super
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Serial Card slot 1..7, a DOS COM number 1..4, or an Amiga `serial.device` unit.
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=== jlSerialOpen
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[source,c]
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----
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bool jlSerialOpen(jlSerialDeviceE device, const jlSerialConfigT *config);
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----
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Opens and configures the port. Only one port may be open at a time; a second
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open without an intervening close fails.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`device` |`jlSerialDeviceE` |Which interface.
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|`config` |`const jlSerialConfigT *` |Line configuration.
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|===
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*Returns:* `true` on success. `false` if the port cannot be opened or the
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platform has no serial support -- and then every other call no-ops.
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=== jlSerialClose
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[source,c]
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----
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void jlSerialClose(void);
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----
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Closes the port and releases its resources. Safe when not open.
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*Parameters:* none. *Returns:* nothing.
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=== jlSerialPoll
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[source,c]
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----
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void jlSerialPoll(void);
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----
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Pumps the receive and transmit buffers. Call once per game frame.
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*Parameters:* none. *Returns:* nothing.
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=== jlSerialAvailable
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[source,c]
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----
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uint16_t jlSerialAvailable(void);
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----
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*Parameters:* none.
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*Returns:* the number of bytes waiting in the receive buffer, readable now
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without blocking.
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=== jlSerialRead
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[source,c]
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----
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uint16_t jlSerialRead(uint8_t *buf, uint16_t max);
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----
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`buf` |`uint8_t *` |Destination buffer.
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|`max` |`uint16_t` |Buffer capacity.
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|===
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*Returns:* the number of bytes copied, 0 to `max`. Never blocks.
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=== jlSerialWrite
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[source,c]
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----
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uint16_t jlSerialWrite(const uint8_t *buf, uint16_t len);
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----
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Sends bytes. Transmit is a bounded poll.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`buf` |`const uint8_t *` |Data to send.
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|`len` |`uint16_t` |Byte count.
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|===
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*Returns:* the number of bytes accepted, which may be fewer than `len` if a
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flow-controlled peer or a full transmit path stalls.
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=== jlSerialWriteByte / jlSerialReadByte
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[source,c]
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----
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bool jlSerialWriteByte(uint8_t b);
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int16_t jlSerialReadByte(void);
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----
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Single-byte convenience calls.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`b` |`uint8_t` |Byte to send.
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|===
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*Returns:* `jlSerialWriteByte` returns `true` if the byte was accepted.
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`jlSerialReadByte` returns the byte, or `-1` when none is ready.
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=== jlSerialFlush
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[source,c]
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----
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void jlSerialFlush(void);
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----
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Discards any buffered received bytes.
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*Parameters:* none. *Returns:* nothing.
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=== jlSerialSetRts
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[source,c]
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----
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void jlSerialSetRts(bool on);
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----
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Asserts or drops RTS, for a caller doing its own receive-side flow control.
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`JL_SERIAL_FLOW_RTSCTS` asks the *port* to handshake; this is the other half --
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the application saying "my buffer is nearly full, stop sending", and later "go
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ahead". That is what a client with a small ring and a peer that can be told to
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pause actually needs.
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[cols="1,1,4", options="header"]
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|===
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|Parameter |Type |Description
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|`on` |`bool` |`true` asserts RTS, meaning ready to receive.
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|===
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*Returns:* nothing. A port with no controllable RTS line no-ops, and a closed
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port no-ops; neither is an error, so this can be driven unconditionally.
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