// Send EOI to PIC outb(0x20, 0x20); In real mode or protected mode, you must set up the IDT (Interrupt Descriptor Table) for IRQ12 (vector 0x2C if PIC is in standard remap). Example for 32-bit protected mode:
if (mouse_cycle == 0) // Byte 0: verify bit 3 = 1 (always set in standard packet) if ((data & 0x08) == 0x08) mouse_packet[0] = data; mouse_cycle = 1; else if (mouse_cycle == 1) mouse_packet[1] = data; mouse_cycle = 2; else if (mouse_cycle == 2) = 0xFFFFFF00; mouse_x += dx; mouse_y -= dy; // Invert Y for screen coordinates mouse_buttons = mouse_packet[0] & 0x07; ps/2 compatible mouse driver
int old_buttons = 0; while (1) Enabling Scroll Wheel (IntelliMouse) Send this sequence to switch to 4-byte packets: // Send EOI to PIC outb(0x20, 0x20); In
The PS/2 mouse might seem like a relic of the 1990s, but it remains the gold standard for low-level OS development. Unlike USB, which relies on complex host controllers and descriptor parsing, the PS/2 interface is simple, memory-mapped, and interrupt-driven. In this article, we’ll build a bare-bones PS/2 mouse driver from scratch, covering initialization, packet decoding, and integration with a simple GUI. 1. Understanding the PS/2 Interface The PS/2 port uses two bidirectional lines: Clock (usually IRQ 12 for the mouse) and Data . Communication is synchronous, with the device sending 11-bit packets (1 start bit, 8 data bits, 1 parity bit, 1 stop bit) when the host pulls the clock low. In this article, we’ll build a bare-bones PS/2
