blocking serial messages

1 files changed, 62 insertions, 0 deletions

diff --git a/src/gpio.zig b/src/gpio.zig
new file mode 100644
index 0000000..ba54394
--- /dev/null
+++ b/src/gpio.zig
@@ -0,0 +1,62 @@
+const PERIPHERAL_BASE = @import("board.zig").PERIPHERAL_BASE;
+
+const FSEL = PERIPHERAL_BASE + 0x200000;
+const SET = PERIPHERAL_BASE + 0x20001c;
+const CLR = PERIPHERAL_BASE + 0x200028;
+const PULL = PERIPHERAL_BASE + 0x2000e4;
+
+const MAX_PIN = 53;
+
+fn call(
+    pin: comptime_int,
+    value: u32,
+    base: comptime_int,
+    field_size: comptime_int,
+) void {
+    const field_mask: u32 = (1 << field_size) - 1;
+
+    if (pin > MAX_PIN) @compileError("invalid pin number");
+
+    const n_fields = 32 / field_size;
+    const reg = base + (pin / n_fields) * 4;
+    const shift = (pin % n_fields) * field_size;
+
+    const mmio_ptr: *volatile u32 = @ptrFromInt(reg);
+    var reg_val = mmio_ptr.*;
+    reg_val &= ~(field_mask << shift);
+    reg_val |= value << shift;
+    mmio_ptr.* = reg_val;
+}
+
+pub fn write(pin: comptime_int, value: bool) void {
+    if (value) {
+        call(pin, 1, SET, 1);
+    } else {
+        call(pin, 1, CLR, 1);
+    }
+}
+
+pub const Pull = enum {
+    none,
+    up,
+    down,
+};
+
+pub fn setPull(pin: comptime_int, pull: Pull) void {
+    call(pin, @intFromEnum(pull), PULL, 2);
+}
+
+pub const Function = enum {
+    input,
+    output,
+    alt5,
+    alt4,
+    alt0,
+    alt1,
+    alt2,
+    alt3,
+};
+
+pub fn setFunction(pin: comptime_int, function: Function) void {
+    call(pin, @intFromEnum(function), FSEL, 3);
+}