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◆ main enhanced-x16-emulator / src / smc.c
4.2 KiB · C · last changed chore(): initial commit 25 days ago source blame history raw
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// Commander X16 Emulator
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// Copyright (c) 2021 Michael Steil
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// All rights reserved. License: 2-clause BSD
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// System Management Controller
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#include <stdio.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include "smc.h"
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#include "glue.h"
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#include "i2c.h"
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#ifdef __EMSCRIPTEN__
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#include <emscripten.h>
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#endif
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// 0x01 0x00      - Power Off
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// 0x01 0x01      - Hard Reboot
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// 0x02 0x00      - Reset Button Press
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// 0x03 0x00      - NMI Button Press
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// 0x04 0x00-0xFF - Power LED Level (PWM)
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// 0x05 0x00-0xFF - Activity LED Level (PWM)
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uint8_t default_read_op = 0x41;
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uint8_t default_read_state = 0;
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uint8_t activity_led;
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uint8_t mse_count = 0;
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#define I2C_DATA_LEN 16
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static uint8_t i2c_data[I2C_DATA_LEN];
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static uint8_t i2c_data_pos = 0;
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bool smc_requested_reset = false;
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void
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smc_i2c_data(uint8_t v) {
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	if (i2c_data_pos < I2C_DATA_LEN) {
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		i2c_data[i2c_data_pos] = v;
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		i2c_data_pos++;
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	}
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}
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uint8_t
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smc_read() {
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	uint8_t mouse_id;
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	uint8_t mouse_size;
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	uint8_t ret;
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	switch (i2c_data[0]){
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		case 0x43: // keycode + mouse
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			if (default_read_state == 0) {
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				default_read_state = 1;
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				ret = i2c_kbd_buffer_next();
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				break;
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			}
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			// fall through
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		case 0x42: // mouse only
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		// fall through
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		// Offset that returns three bytes from mouse buffer (one movement packet) or a single zero if there is not complete packet in the buffer
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		// mse_count keeps track of which one of the three bytes it's sending
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		case 0x21:
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			mouse_id = mouse_get_device_id();
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			if (mouse_id == 3 || mouse_id == 4) {
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				mouse_size = 4;
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			}
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			else {
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				mouse_size = 3;
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			}
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			if (mse_count == 0 && i2c_mse_buffer_count() >= mouse_size) {		// If start of packet, check if there are at least three bytes in the buffer
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				mse_count++;
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				ret = i2c_mse_buffer_next();
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			}
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			else if (mse_count > 0) {								// If we have already started sending bytes, assume there is enough data in the buffer
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				mse_count++;
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				if (mse_count == mouse_size) {
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					mse_count = 0;
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					default_read_state = 0;
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				}
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				ret = i2c_mse_buffer_next();
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			}
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			else {													// Return a single zero if no complete packet available
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				mse_count = 0;
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				default_read_state = 0;
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				ret = 0x00;
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			}
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			break;
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		case 0x41: // keycode only
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			default_read_state = 0;
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			// fall through
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		// Offset that returns one byte from the keyboard buffer
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		case 0x07:
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			ret = i2c_kbd_buffer_next();
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			break;
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		// Offset, initially used for debugging in the SMC, but now
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		// also used to inform kernal whether power on was done by
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		// holding the power button
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		case 0x09:
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			if (pwr_long_press) {
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				// Reset pwr_long_press so a reset will start normally
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				pwr_long_press = false;
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				ret = 1;
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			} else {
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				ret = 0;
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			}
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			break;
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		case 0x22:
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			ret = mouse_get_device_id();
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			break;
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		case 0x30:
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			ret = SMC_VERSION_MAJOR;
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			break;
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		case 0x31:
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			ret = SMC_VERSION_MINOR;
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			break;
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		case 0x32:
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			ret = SMC_VERSION_PATCH;
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			break;
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		default:
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			ret = 0xff;
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	}
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	i2c_data[0] = default_read_op;
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	i2c_data_pos = 0;
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	return ret;
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}
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void
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smc_write() {
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	switch (i2c_data[0]) {
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		case 1:
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			if (i2c_data[1] == 0) {
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				printf("SMC Power Off.\n");
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				main_shutdown();
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#ifdef __EMSCRIPTEN__
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				emscripten_force_exit(0);
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#endif
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				exit(0);
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			} else if (i2c_data[1] == 1) {
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				smc_requested_reset = true;
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			}
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			break;
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		case 2:
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			if (i2c_data[1] == 0) {
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				smc_requested_reset = true;
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			}
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			break;
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		case 3:
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			if (i2c_data[1] == 0) {
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				nmi6502();
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			}
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			break;
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		case 4:
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			// Power LED is not controllable
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			break;
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		case 5:
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			activity_led = i2c_data[1] >= 128 ? 255 : 0;
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			break;
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		case 0x20:
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			mouse_set_device_id(i2c_data[1]);
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			break;
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		case 0x40:
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			default_read_op = i2c_data[1];
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			default_read_state = 0;
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			break;
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	}
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	i2c_data[0] = default_read_op;
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	i2c_data_pos = 0;
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}
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// Side-effect-free snapshot of SMC state for the ImGui debugger.
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void
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smc_debug_get_state(smc_debug_state_t *out)
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{
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	out->default_read_op  = default_read_op;
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	out->activity_led     = activity_led;
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	out->i2c_data_pos     = i2c_data_pos;
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	out->mse_count        = mse_count;
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	out->requested_reset  = smc_requested_reset;
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	for (int i = 0; i < I2C_DATA_LEN; i++) {
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		out->i2c_data[i] = i2c_data[i];
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	}
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	out->kbd_fill = i2c_kbd_buffer_count();
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	out->mse_fill = i2c_mse_buffer_count();
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}
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