Avr fixes (#36)

* Makes AVR UART work.

Co-authored-by: Felix "xq" Queißner <git@masterq32.de>

src/modules/chips/atmega328p/atmega328p.zig

@@ -1,6 +1,8 @@
 const std = @import("std");
 const micro = @import("microzig");
+
 pub usingnamespace @import("registers.zig");
+const regz = @import("registers.zig").registers;
 
 pub const cpu = micro.cpu;
 const Port = enum(u8) {
@@ -26,13 +28,15 @@ pub fn parsePin(comptime spec: []const u8) type {
 pub const gpio = struct {
     fn regs(comptime desc: type) type {
         return struct {
-            const pin_addr = 3 * @enumToInt(desc.port) + 0x00;
+            // io address
-            const dir_addr = 3 * @enumToInt(desc.port) + 0x01;
+            const pin_addr: u5 = 3 * @enumToInt(desc.port) + 0x00;
-            const port_addr = 3 * @enumToInt(desc.port) + 0x02;
+            const dir_addr: u5 = 3 * @enumToInt(desc.port) + 0x01;
+            const port_addr: u5 = 3 * @enumToInt(desc.port) + 0x02;
 
-            const pin = @intToPtr(*volatile u8, pin_addr);
+            // ram mapping
-            const dir = @intToPtr(*volatile u8, dir_addr);
+            const pin = @intToPtr(*volatile u8, 0x20 + @as(usize, pin_addr));
-            const port = @intToPtr(*volatile u8, port_addr);
+            const dir = @intToPtr(*volatile u8, 0x20 + @as(usize, dir_addr));
+            const port = @intToPtr(*volatile u8, 0x20 + @as(usize, port_addr));
         };
     }
 
@@ -63,3 +67,116 @@ pub const gpio = struct {
         cpu.sbi(regs(pin).pin_addr, pin.pin);
     }
 };
+
+pub const uart = struct {
+    pub const DataBits = enum {
+        five,
+        six,
+        seven,
+        eight,
+        nine,
+    };
+
+    pub const StopBits = enum {
+        one,
+        two,
+    };
+
+    pub const Parity = enum {
+        odd,
+        even,
+    };
+};
+
+pub fn Uart(comptime index: usize) type {
+    if (index != 0) @compileError("Atmega328p only has a single uart!");
+    return struct {
+        const Self = @This();
+
+        fn computeDivider(baud_rate: u32) !u12 {
+            const pclk = micro.clock.get();
+            const divider = ((pclk + (8 * baud_rate)) / (16 * baud_rate)) - 1;
+
+            return std.math.cast(u12, divider) catch return error.UnsupportedBaudRate;
+        }
+
+        fn computeBaudRate(divider: u12) u32 {
+            return micro.clock.get() / (16 * @as(u32, divider) + 1);
+        }
+
+        pub fn init(config: micro.uart.Config) !Self {
+            const ucsz: u3 = switch (config.data_bits) {
+                .five => 0b000,
+                .six => 0b001,
+                .seven => 0b010,
+                .eight => 0b011,
+                .nine => return error.UnsupportedWordSize, // 0b111
+            };
+
+            const upm: u2 = if (config.parity) |parity| switch (parity) {
+                .even => @as(u2, 0b10), // even
+                .odd => @as(u2, 0b11), // odd
+            } else 0b00; // parity disabled
+
+            const usbs: u1 = switch (config.stop_bits) {
+                .one => 0b0,
+                .two => 0b1,
+            };
+
+            const umsel: u2 = 0b00; // Asynchronous USART
+
+            // baud is computed like this:
+            //             f(osc)
+            // BAUD = ----------------
+            //        16 * (UBRRn + 1)
+
+            const ubrr_val = try computeDivider(config.baud_rate);
+
+            regz.USART0.UCSR0A.modify(.{
+                .MPCM0 = 0,
+                .U2X0 = 0,
+            });
+            regz.USART0.UCSR0B.write(.{
+                .TXB80 = 0, // we don't care about these btw
+                .RXB80 = 0, // we don't care about these btw
+                .UCSZ02 = @truncate(u1, (ucsz & 0x04) >> 2),
+                .TXEN0 = 1,
+                .RXEN0 = 1,
+                .UDRIE0 = 0, // no interrupts
+                .TXCIE0 = 0, // no interrupts
+                .RXCIE0 = 0, // no interrupts
+            });
+            regz.USART0.UCSR0C.write(.{
+                .UCPOL0 = 0, // async mode
+                .UCSZ0 = @truncate(u2, (ucsz & 0x03) >> 0),
+                .USBS0 = usbs,
+                .UPM0 = upm,
+                .UMSEL0 = umsel,
+            });
+
+            regz.USART0.UBRR0.modify(ubrr_val);
+
+            return Self{};
+        }
+
+        pub fn canWrite(self: Self) bool {
+            _ = self;
+            return (regz.USART0.UCSR0A.read().UDRE0 == 1);
+        }
+
+        pub fn tx(self: Self, ch: u8) void {
+            while (!self.canWrite()) {} // Wait for Previous transmission
+            regz.USART0.UDR0.* = ch; // Load the data to be transmitted
+        }
+
+        pub fn canRead(self: Self) bool {
+            _ = self;
+            return (regz.USART0.UCSR0A.read().RXC0 == 1);
+        }
+
+        pub fn rx(self: Self) u8 {
+            while (!self.canRead()) {} // Wait till the data is received
+            return regz.USART0.UDR0.*; // Read received data
+        }
+    };
+}

src/modules/chips/atmega328p/registers.zig

@@ -279,7 +279,7 @@ pub const registers = struct {
 
         /// address: 0xc4
         /// USART Baud Rate Register Bytes
-        pub const UBRR0 = @intToPtr(*volatile u12, 0xc4);
+        pub const UBRR0 = @intToPtr(*volatile MmioInt(16, u12), 0xc4);
     };
 
     /// Two Wire Serial Interface
@@ -1110,7 +1110,7 @@ pub const registers = struct {
 
         /// address: 0x5d
         /// Stack Pointer
-        pub const SP = @intToPtr(*volatile u12, 0x5d);
+        pub const SP = @intToPtr(*volatile MmioInt(16, u12), 0x5d);
 
         /// address: 0x57
         /// Store Program Memory Control and Status Register