From 49fce9c584d0e57d45b8b83d2e5ee513110a17fb Mon Sep 17 00:00:00 2001
From: torque <torque@epicyclic.dev>
Date: Mon, 1 Jul 2024 23:55:56 -0700
Subject: [PATCH] start writing control and config functionality

This is not hooked up and does nothing notable, yet. Soon there will
probably be something to test with hardware, though.
---
 src/Config.zig                   |  88 ++++++++++
 src/LabjackYaesu.zig             | 250 +++++++++++++++++++++++++++
 src/RotCtl.zig                   | 288 +++++++++++++++++++++++++++++++
 src/{ljacklm.zig => labjack.zig} |  62 ++++++-
 src/main.zig                     |  14 +-
 5 files changed, 689 insertions(+), 13 deletions(-)
 create mode 100644 src/Config.zig
 create mode 100644 src/LabjackYaesu.zig
 create mode 100644 src/RotCtl.zig
 rename src/{ljacklm.zig => labjack.zig} (92%)

diff --git a/src/Config.zig b/src/Config.zig
new file mode 100644
index 0000000..421f235
--- /dev/null
+++ b/src/Config.zig
@@ -0,0 +1,88 @@
+const std = @import("std");
+
+const AzEl = @import("./LabjackYaesu.zig").AzEl;
+const lj = @import("./labjack.zig");
+
+const Config = @This();
+
+var global_internal: Config = undefined;
+pub const global: *const Config;
+
+pub fn load(allocator: std.mem.Allocator, reader: anytype) !void {
+    var jread = std.json.Reader(1024, @TypeOf(reader)).init(allocator, reader);
+    defer jread.deinit();
+
+    global_internal = try std.json.parseFromTokenSourceLeaky(allocator, &jread, .{});
+}
+
+labjack: LabjackConfig = .{
+    .device = .autodetect,
+    .feedback_calibration = .{
+        .azimuth = .{
+            .minimum = .{ .voltage = 0.0, .angle = 0.0 },
+            .maximum = .{ .voltage = 5.0, .angle = 450.0 },
+        },
+        .elevation = .{
+            .minimum = .{ .voltage = 0.0, .angle = 0.0 },
+            .maximum = .{ .voltage = 5.0, .angle = 180.0 },
+        },
+    },
+},
+controller: ControllerConfig = .{
+    .azimuth_input = .{ .channel = .diff_01, .gain_index = 2 },
+    .elevation_input = .{ .channel = .diff_23, .gain_index = 2 },
+    .azimuth_outputs = .{ .increase = .{ .io = 0 }, .decrease = .{ .io = 1 } },
+    .elevation_outputs = .{ .increase = .{ .io = 2 }, .decrease = .{ .io = 3 } },
+    .loop_interval_ns = 50_000_000,
+    .parking_posture = .{ .azimuth = 180, .elevation = 90 },
+    .angle_tolerance = .{ .azimuth = 1, .elevation = 1 },
+},
+
+pub const VoltAngle = struct { voltage: f64, angle: f64 };
+pub const MinMax = struct {
+    minimum: VoltAngle,
+    maximum: VoltAngle,
+
+    pub inline fn slope(self: MinMax) f64 {
+        return self.angleDiff() / self.voltDiff();
+    }
+
+    pub inline fn voltDiff(self: MinMax) f64 {
+        return self.maximum.voltage - self.minimum.voltage;
+    }
+
+    pub inline fn angleDiff(self: MinMax) f64 {
+        return self.maximum.angle - self.minimum.angle;
+    }
+};
+
+const LabjackConfig = struct {
+    device: union(enum) {
+        autodetect,
+        serial_number: i32,
+    },
+    // Very basic two-point calibration for each degree of freedom. All other angles are
+    // linearly interpolated from these two points. This assumes the feedback is linear,
+    // which seems to be a mostly reasonable assumption in practice.
+    feedback_calibration: struct {
+        azimuth: MinMax,
+        elevation: MinMax,
+    },
+};
+
+const ControllerConfig = struct {
+    azimuth_input: lj.AnalogInput,
+    elevation_input: lj.AnalogInput,
+
+    azimuth_outputs: OutPair,
+    elevation_outputs: OutPair,
+
+    loop_interval_ns: u64,
+    parking_posture: AzEl,
+    angle_tolerance: AzEl,
+
+    const OutPair = struct {
+        increase: lj.DigitalOutputChannel,
+        decrease: lj.DigitalOutputChannel,
+    };
+};
diff --git a/src/LabjackYaesu.zig b/src/LabjackYaesu.zig
new file mode 100644
index 0000000..8c0603a
--- /dev/null
+++ b/src/LabjackYaesu.zig
@@ -0,0 +1,250 @@
+const std = @import("std");
+
+const lj = @import("./labjack.zig");
+const Config = @import("./Config.zig");
+const config = Config.global;
+
+const LabjackYaesu = @This();
+
+control_thread: std.Thread,
+lock: *std.Thread.Mutex,
+controller: *const Controller,
+
+pub const AzEl = struct {
+    azimuth: f64,
+    elevation: f64,
+};
+
+pub fn init(allocator: std.mem.Allocator) !LabjackYaesu {
+    const lock = try allocator.create(std.Thread.Mutex);
+    errdefer allocator.destroy(lock);
+    lock.* = .{};
+
+    const controller = try allocator.create(Controller);
+    errdefer allocator.destroy(controller);
+    controller.init(lock);
+    // do this in the main thread so we can throw the error about it synchronously.
+    try controller.connectLabjack();
+
+    return .{
+        .control_thread = try std.Thread.spawn(.{}, runController, .{controller}),
+        .lock = lock,
+        .controller = controller,
+    };
+}
+
+pub fn setTarget(self: LabjackYaesu, target: AzEl) void {
+    self.lock.lock();
+    defer self.lock.unlock();
+
+    const controller = @constCast(self.controller);
+    controller.target = target;
+    controller.requested_state = .running;
+}
+
+pub fn startCalibration(self: LabjackYaesu) void {
+    // there are two different types of calibration:
+    // 1. feedback calibration, running to the extents of the rotator
+    // 2. sun calibration, which determines the azimuth and elevation angle
+    //    offset between the rotator's physical stops and geodetic north
+    //
+    // The former is (fairly) trivial to automate, just run until stall
+    // (assuming there's no deadband in the feedback). The latter requires
+    // manual input as the human is the feedback hardware in the loop.
+}
+
+pub fn idle(self: LabjackYaesu) void {
+    self.lock.lock();
+    defer self.lock.unlock();
+
+    controller.requested_state = .idle;
+}
+
+pub fn stop(self: LabjackYaesu) void {
+    self.lock.lock();
+    defer self.lock.unlock();
+
+    controller.requested_state = .stopped;
+}
+
+fn runController(controller: *Controller) void {
+    controller.run() catch {};
+}
+
+const Controller = struct {
+    target: AzEl,
+    position: AzEl,
+
+    current_state: ControllerState,
+    requested_state: ControllerState,
+
+    lock: *std.Thread.Mutex,
+    labjack: lj.Labjack,
+
+    const ControllerState = enum {
+        initializing,
+        idle,
+        calibration,
+        running,
+        stopped,
+    };
+
+    fn init(self: *Controller, lock: *std.Thread.Mutex) void {
+        self.* = .{
+            .target = .{ .azimuth = 0, .elevation = 0 },
+            .position = .{ .azimuth = 0, .elevation = 0 },
+            .state = .stopped,
+            .requested_state = .idle,
+            .lock = lock,
+            .labjack = switch (config.labjack.device) {
+                .autodetect => try labjack.Labjack.autodetect(),
+                .serial_number => |sn| labjack.Labjack.with_serial_number(sn),
+            },
+        };
+    }
+
+    fn connectLabjack(self: *Controller) !void {
+        const info = try controller.labjack.connect();
+        controller.labjack.id = info.local_id;
+    }
+
+    fn lerpOne(input: f64, cal_points: Config.MinMax) f64 {
+        return (input - cal_points.minimum.voltage) * cal_points.slope() + cal_points.minimum.angle;
+    }
+
+    fn lerpAngles(input: [2]lj.AnalogReadResult) AzEl {
+        return .{
+            .azimuth = lerpOne(input[0].voltage, config.labjack.feedback_calibration.azimuth),
+            .elevation = lerpOne(input[1].voltage, config.labjack.feedback_calibration.elevation),
+        };
+    }
+
+    fn signDeadzone(offset: f64, deadzone: f64) enum { negative, zero, positive } {
+        return if (@abs(offset) < deadzone)
+            .zero
+        else if (offset < 0)
+            .negative
+        else
+            .positive;
+    }
+
+    fn updateAzEl(self: *const Controller) !AzEl {
+        const inputs = .{ config.controller.azimuth_input, config.controller.elevation_input };
+
+        const raw = try self.labjack.readAnalogWriteDigital(
+            2,
+            inputs,
+            .{false} ** 4,
+            true,
+        );
+
+        return lerpAngles(raw);
+    }
+
+    fn drive(self: *const Controller, pos_error: AzEl) !AzEl {
+        // NOTE: feedback will be roughly config.controller.loop_interval_ns out of
+        //       date. For high loop rates, this shouldn't be an issue.
+
+        const inputs = .{ config.controller.azimuth_input, config.controller.elevation_input };
+        var drive_signal: [4]bool = .{false} ** 4;
+
+        const azsign = signDeadzone(
+            pos_error.azimuth,
+            config.controller.angle_tolerance.azimuth,
+        );
+
+        const elsign = signDeadzone(
+            pos_error.elevation,
+            config.controller.angle_tolerance.elevation,
+        );
+
+        drive_signal[config.azimuth_outputs.increase.io] = azsign == .positive;
+        drive_signal[config.azimuth_outputs.decrease.io] = azsign == .negative;
+        drive_signal[config.elevation_outputs.increase.io] = elsign == .positive;
+        drive_signal[config.elevation_outputs.decrease.io] = elsign == .negative;
+
+        const raw = try self.labjack.readAnalogWriteDigital(2, inputs, drive_signal, true);
+
+        return lerpAngles(raw);
+    }
+
+    fn run(self: *Controller) !void {
+        self.state = .initializing;
+
+        var timer: LoopTimer = .{ .interval_ns = config.controller.loop_interval_ns };
+
+        while (timer.mark()) : (timer.sleep()) switch (self.state) {
+            .initializing, .idle => {
+                const pos = self.updateAzEl() catch {
+                    self.lock.lock();
+                    defer self.lock.unlock();
+
+                    self.state = .stopped;
+                    continue;
+                };
+
+                self.lock.lock();
+                defer self.lock.unlock();
+
+                self.position = pos;
+                self.state = self.requested_state;
+            },
+            .calibration => {
+                self.lock.lock();
+                defer self.lock.unlock();
+
+                // run calibration routine. psych, this does nothing. gottem
+                self.state = .idle;
+                self.requested_state = self.state;
+            },
+            .running => {
+                const pos_error: AzEl = blk: {
+                    self.lock.lock();
+                    defer self.lock.unlock();
+
+                    break :blk .{
+                        .azimuth = self.target.azimuth - self.position.azimuth,
+                        .elevation = self.target.elevation - self.position.elevation,
+                    };
+                };
+
+                const pos = self.drive(pos_error) catch {
+                    self.lock.lock();
+                    defer self.lock.unlock();
+
+                    self.state = .stopped;
+                    continue;
+                };
+
+                self.lock.lock();
+                defer self.lock.unlock();
+
+                self.position = pos;
+                self.state = self.requested_state;
+            },
+            .stopped => {
+                // attempt to reset the drive outputs
+                _ = self.updateAzEl() catch {};
+                break;
+            },
+        };
+    }
+};
+
+pub const LoopTimer = struct {
+    interval_ns: u64,
+
+    start: i128 = 0,
+
+    pub fn mark(self: *LoopTimer) bool {
+        self.start = std.time.nanoTimestamp();
+        return true;
+    }
+
+    pub fn sleep(self: *LoopTimer) void {
+        const now = std.time.nanoTimestamp();
+        const elapsed: u64 = @intCast(now - self.start);
+
+        std.time.sleep(interval_ns - elapsed);
+    }
+};
diff --git a/src/RotCtl.zig b/src/RotCtl.zig
new file mode 100644
index 0000000..9b81a41
--- /dev/null
+++ b/src/RotCtl.zig
@@ -0,0 +1,288 @@
+const std = @import("std");
+
+const LabjackYaesu = @import("./LabjackYaesu.zig");
+
+const RotCtl = @This();
+
+const log = std.log.scoped(.RotCtl);
+
+writer: std.io.BufferedWriter(512, std.net.Stream.Writer),
+running: bool,
+rotator: LabjackYaesu,
+
+pub fn run() !void {
+    var server = std.net.StreamServer.init(.{ .reuse_address = true });
+    defer server.deinit();
+
+    const listen_addr = try std.net.Address.parseIp(
+        config.gpredict_listen_address,
+        config.gpredict_listen_port,
+    );
+    server.listen(listen_addr) catch {
+        log.err("Could not listen on {}. Is it already in use?", .{listen_addr});
+        return;
+    };
+    log.info("Listening for client on: {}", .{listen_addr});
+
+    var interface: RotCtl = .{
+        .writer = undefined,
+        .running = true,
+        .rotator = LabjackYaesu.init(),
+    };
+
+    while (true) {
+        const client = try server.accept();
+        defer {
+            log.info("disconnecting client", .{});
+            client.stream.close();
+        }
+
+        interface.writer = .{ .unbuffered_writer = client.stream.writer() };
+        interface.running = true;
+        defer interface.running = false;
+
+        log.info("client connected from {}", .{client.address});
+
+        var readbuffer = [_]u8{0} ** 512;
+        var fbs = std.io.fixedBufferStream(&readbuffer);
+        const reader = client.stream.reader();
+
+        while (interface.running) : (fbs.reset()) {
+            reader.streamUntilDelimiter(fbs.writer(), '\n', readbuffer.len) catch break;
+            try radio.handleHamlibCommand(fbs.getWritten());
+        }
+    }
+}
+
+fn write(self: *const Hamlibber, buf: []const u8) !void {
+    try self.writer.writeAll(buf);
+}
+
+fn replyStatus(self: *RadioProxy, comptime status: HamlibErrorCode) !void {
+    try self.write(comptime status.replyFrame() ++ "\n");
+}
+
+fn handleHamlibCommand(
+    self: *const Hamlibber,
+    command: []const u8,
+) !void {
+    var tokens = std.mem.tokenizeScalar(u8, command, ' ');
+
+    const first = tokens.next().?;
+    if (first.len == 1 or first[0] == '\\') {
+        switch (first[0]) {
+            'F' => {
+                const freqt = tokens.next() orelse
+                    return self.replyStatus(.invalid_parameter);
+
+                const new = std.fmt.parseInt(i32, freqt, 10) catch
+                    return self.replyStatus(.invalid_parameter);
+
+                self.setFrequency(new) catch
+                    return self.replyStatus(.io_error);
+
+                try self.replyStatus(.okay);
+            },
+            'f' => {
+                const freq = self.getFrequency() catch
+                    return self.replyStatus(.io_error);
+
+                try self.print("{d}", .{freq});
+            },
+            't' => {
+                try self.print("{d}", .{@intFromBool(self.ptt_state)});
+            },
+            'q' => {
+                self.running = false;
+                self.replyStatus(.okay) catch return;
+            },
+            '\\' => return self.parseLongCommand(first[1..], &tokens),
+            // zig fmt: off
+             '*',  '1',  '2',  '4',  '_',  'A',  'a',  'B',  'b',  'C',  'c',  'D',
+             'd',  'E',  'e',  'G',  'g',  'H',  'h',  'I',  'i',  'J',  'j',  'L',
+             'l',  'M',  'm',  'N',  'n',  'O',  'o',  'P',  'p',  'R',  'r',  'S',
+             's',  'T',  'U',  'u',  'V',  'v',  'X',  'x',  'Y',  'y',  'Z',  'z',
+            0x87, 0x88, 0x89, 0x8A, 0x8B, 0x90, 0x91, 0x92, 0x93, 0xF3, 0xF5
+            => |cmd| {
+                log.warn("Unsupported command {c}", .{cmd});
+                try self.replyStatus(.not_supported);
+            },
+                // zig fmt: on
+            else => |cmd| {
+                log.err("unknown command {}", .{cmd});
+                try self.replyStatus(.not_implemented);
+            },
+        }
+    } else if (std.mem.eql(u8, first, "AOS")) {
+        // gpredict just kind of shoves this message in on top of the HamLib
+        // protocol.
+        log.info("Received AOS message from gpredict", .{});
+        self.setFrequency(self.base_freq) catch return self.replyStatus(.io_error);
+        try self.replyStatus(.okay);
+    } else if (std.mem.eql(u8, first, "LOS")) {
+        log.info("Received LOS message from gpredict", .{});
+        if (self.stop_on_los) {
+            self.running = false;
+            self.setFrequency(self.base_freq) catch return self.replyStatus(.io_error);
+        }
+        try self.replyStatus(.okay);
+    } else try self.replyStatus(.not_supported);
+}
+
+fn parseLongCommand(
+    self: *RadioProxy,
+    command: []const u8,
+    tokens: *std.mem.TokenIterator(u8, .scalar),
+) !void {
+    _ = tokens;
+
+    for (hamlib_commands) |check| {
+        if (command.len >= check.long.len and std.mem.eql(u8, check.long, command[0..check.long.len])) {
+            log.warn("Unsupported command {s}", .{command});
+            break;
+        }
+    } else {
+        log.warn("Unknown command {s}", .{command});
+    }
+    return self.replyStatus(.not_supported);
+}
+
+fn resetWatchdog(self: *RadioProxy) !void {
+    const wd = spacecraft.shared.commands.watchdog;
+
+    const reqheader = csp.Header{
+        .priority = 1,
+        .source = Config.global.doppler_shift.gs_source_address,
+        .destination = Config.global.doppler_shift.gs_radio_address,
+        .destination_port = @intFromEnum(wd.Reset.port),
+        .source_port = self.reqPort(),
+    };
+
+    const request = wd.Reset{};
+    const packet = reqheader.packBig() ++ request.packLittle();
+
+    try self.nats.publish(self.nats_up, &packet);
+
+    while (true) {
+        const res = self.nats_down.nextMessage(reply_timeout) catch |err| {
+            log.err("Could not reset ground UHF radio watchdog. Is the radio on and bridged to NATS?", .{});
+            return err;
+        };
+        const data = res.getData() orelse continue;
+        if (data.len != csp.Header.pack_size + wd.Reset.Response.pack_size)
+            continue;
+
+        const resheader = csp.Header.unpackBig(data[0..csp.Header.pack_size].*);
+        if (!resheader.isReply(reqheader)) continue;
+
+        const reply = wd.Reset.Response.unpackLittle(
+            data[csp.Header.pack_size..][0..wd.Reset.Response.pack_size].*,
+        );
+        if (reply.err != .okay) {
+            log.err("Got error response for ground UHF watchdog reset: {}", .{reply.err.code()});
+            return error.Failure;
+        }
+        break;
+    }
+
+    log.info("Successfully reset the ground UHF radio watchdog timer.", .{});
+}
+
+const HamlibErrorCode = enum(u8) {
+    okay = 0,
+    invalid_parameter = 1,
+    invalid_configuration = 2,
+    out_of_memory = 3,
+    not_implemented = 4,
+    timeout = 5,
+    io_error = 6,
+    internal_error = 7,
+    protocol_error = 8,
+    command_rejected = 9,
+    parameter_truncated = 10,
+    not_supported = 11,
+    not_targetable = 12,
+    bus_error = 13,
+    bus_busy = 14,
+    invalid_arg = 15,
+    invalid_vfo = 16,
+    domain_error = 17,
+    deprecated = 18,
+    security = 19,
+    power = 20,
+
+    fn replyFrame(comptime self: HamlibErrorCode) []const u8 {
+        return std.fmt.comptimePrint(
+            "RPRT {d}",
+            .{-@as(i8, @intCast(@intFromEnum(self)))},
+        );
+    }
+};
+
+const HamlibCommand = struct {
+    short: ?u8 = null,
+    long: ?[]const u8 = null,
+    mode: enum { rotator, radio, both },
+};
+
+const hamlib_commands = [_]HamlibCommand{
+    .{ .short = 'F', .long = "set_freq", .mode = .radio },
+    .{ .short = 'f', .long = "get_freq", .mode = .radio },
+    .{ .short = 'T', .long = "set_ptt", .mode = .radio },
+    .{ .short = 't', .long = "get_ptt", .mode = .radio },
+    .{ .short = 'q', .mode = .both }, // quit
+    .{ .short = 'Q', .mode = .both }, // quit
+    .{ .short = 'P', .long = "set_pos", .mode = .rotator }, // azimuth: f64, elevation: f64
+    .{ .short = 'p', .long = "get_pos", .mode = .rotator }, // return az: f64, el: f64
+    .{ .short = 'M', .long = "move", .mode = .rotator }, // direction: enum { up=2, down=4, left=8, right=16 }, speed: i8 (0-100 or -1)
+    .{ .short = 'S', .long = "stop", .mode = .rotator },
+    .{ .short = 'K', .long = "park", .mode = .rotator },
+    .{ .short = 'C', .long = "set_conf", .mode = .rotator }, // token: []const u8, value: []const u8
+    .{ .short = 'R', .long = "reset", .mode = .rotator }, // u1 (1 is reset all)
+    .{ .short = '_', .long = "get_info", .mode = .rotator }, // return Model name
+    .{ .short = 'K', .long = "park", .mode = .rotator },
+    .{ .long = "dump_state", .mode = .rotator }, // ???
+    .{ .short = '1', .long = "dump_caps", .mode = .rotator }, // ???
+    .{ .short = 'w', .long = "send_cmd", .mode = .rotator }, // []const u8, send serial command directly to the rotator
+    .{ .short = 'L', .long = "lonlat2loc", .mode = .rotator }, // return Maidenhead locator for given long: f64 and lat: f64, locator precision: u4 (2-12)
+    .{ .short = 'l', .long = "loc2lonlat", .mode = .rotator }, //  the inverse of the above
+    .{ .short = 'D', .long = "dms2dec", .mode = .rotator }, // deg, min, sec, 0 (positive) or 1 (negative)
+    .{ .short = 'd', .long = "dec2dms", .mode = .rotator },
+    .{ .short = 'E', .long = "dmmm2dec", .mode = .rotator },
+    .{ .short = 'e', .long = "dec2dmmm", .mode = .rotator },
+    .{ .short = 'B', .long = "grb", .mode = .rotator },
+    .{ .short = 'A', .long = "a_sp2a_lp", .mode = .rotator },
+    .{ .short = 'a', .long = "d_sp2d_lp", .mode = .rotator },
+    .{ .long = "pause", .mode = .rotator },
+};
+
+// D, dms2dec 'Degrees' 'Minutes' 'Seconds' 'S/W'
+// Returns 'Dec Degrees', a signed floating point value.
+// 'Degrees' and 'Minutes' are integer values.
+// 'Seconds' is a floating point value.
+// 'S/W' is a flag with ’1’ indicating South latitude or West longitude and ’0’ North or East (the flag is needed as computers don’t recognize a signed zero even though only the 'Degrees' value is typically signed in DMS notation).
+// d, dec2dms 'Dec Degrees'
+// Returns 'Degrees' 'Minutes' 'Seconds' 'S/W'.
+// Values are as in dms2dec above.
+// E, dmmm2dec 'Degrees' 'Dec Minutes' 'S/W'
+// Returns 'Dec Degrees', a signed floating point value.
+// 'Degrees' is an integer value.
+// 'Dec Minutes' is a floating point value.
+// 'S/W' is a flag as in dms2dec above.
+// e, dec2dmmm 'Dec Deg'
+// Returns 'Degrees' 'Minutes' 'S/W'.
+// Values are as in dmmm2dec above.
+// B, qrb 'Lon 1' 'Lat 1' 'Lon 2' 'Lat 2'
+// Returns 'Distance' and 'Azimuth'.
+// 'Distance' is in km.
+// 'Azimuth' is in degrees.
+// Supplied Lon/Lat values are signed floating point numbers.
+// A, a_sp2a_lp 'Short Path Deg'
+// Returns 'Long Path Deg'.
+// Both the supplied argument and returned value are floating point values within the range of 0.00 to 360.00.
+// Note: Supplying a negative value will return an error message.
+// a, d_sp2d_lp 'Short Path km'
+// Returns 'Long Path km'.
+// Both the supplied argument and returned value are floating point values.
+// pause 'Seconds'
+// Pause for the given whole (integer) number of 'Seconds' before sending the next command to the rotator.
diff --git a/src/ljacklm.zig b/src/labjack.zig
similarity index 92%
rename from src/ljacklm.zig
rename to src/labjack.zig
index c25892e..950ae10 100644
--- a/src/ljacklm.zig
+++ b/src/labjack.zig
@@ -5,13 +5,27 @@ pub fn getDriverVersion() f32 {
 }
 
 pub const Labjack = struct {
-    id: ?u32 = null,
+    id: ?i32 = null,
     demo: bool = false,
 
     pub fn autodetect() Labjack {
         return .{};
     }
 
+    pub fn with_serial_number(sn: i32) Labjack {
+        return .{ .id = sn };
+    }
+
+    pub fn connect(self: Labjack) LabjackError!struct { local_id: i32, firmware_version: f32 } {
+        var id = self.cId();
+        const version = c_api.GetFirmwareVersion(&id);
+
+        return if (version == 0)
+            @as(c_api.LabjackCError, @bitCast(id)).toError()
+        else
+            .{ .local_id = @intCast(id), .firmware_version = version };
+    }
+
     pub fn firmwareVersion(self: Labjack) LabjackError!f32 {
         var id = self.cId();
         const version = c_api.GetFirmwareVersion(&id);
@@ -24,7 +38,7 @@ pub const Labjack = struct {
 
     /// Read one analog input channel, either single-ended or differential
     pub fn analogReadOne(self: Labjack, input: AnalogInput) LabjackError!AnalogReadResult {
-        if (!input.channel.isDifferential() and input.gain != 0) {
+        if (!input.channel.isDifferential() and input.gain_index != 0) {
             return error.InvalidGain;
         }
 
@@ -36,7 +50,7 @@ pub const Labjack = struct {
             &id,
             @intFromBool(self.demo),
             input.channelNumber(),
-            input.gain,
+            input.gain_index,
             &over_v,
             &res.voltage,
         );
@@ -79,7 +93,7 @@ pub const Labjack = struct {
         var gains: [incount]c_long = undefined;
         for (inputs, &in_channels, &gains) |from, *inc, *gain| {
             inc.* = from.channelNumber();
-            gain.* = from.gain;
+            gain.* = from.gain_index;
         }
         var v_out: [4]f32 = .{0} ** 4;
         var over_v: c_long = 0;
@@ -119,7 +133,7 @@ pub const Labjack = struct {
 
 pub const AnalogInput = struct {
     channel: AnalogInputChannel,
-    gain: Gain = 0,
+    gain_index: GainIndex = 0,
 
     pub fn channelNumber(self: AnalogInput) u4 {
         return @intFromEnum(self.channel);
@@ -191,7 +205,7 @@ pub const DigitalOutputChannel = union(enum) {
 // 5 => G=10 ±2 volts
 // 6 => G=16 ±1.25 volts
 // 7 => G=20 ±1 volt
-pub const Gain = u3;
+pub const GainIndex = u3;
 
 pub const PackedOutput = packed struct(u4) {
     io0: bool,
@@ -199,6 +213,18 @@ pub const PackedOutput = packed struct(u4) {
     io2: bool,
     io3: bool,
 
+    pub fn setOut(self: *PackedOutput, output: DigitalOutput) !void {
+        switch (output) {
+            .io => |num| switch (num) {
+                0 => self.io0 = output.level,
+                1 => self.io1 = output.level,
+                2 => self.io2 = output.level,
+                3 => self.io3 = output.level,
+            },
+            .d => return error.Invalid,
+        }
+    }
+
     pub fn fromBoolArray(states: [4]bool) PackedOutput {
         return .{
             .io0 = states[0],
@@ -214,6 +240,30 @@ pub const PackedOutput = packed struct(u4) {
 };
 
 pub const c_api = struct {
+    pub const vendor_id: u16 = 0x0CD5;
+    pub const u12_product_id: u16 = 0x0001;
+
+    pub extern fn OpenLabJack(
+        errorcode: *LabjackCError,
+        vendor_id: c_uint,
+        product_id: c_uint,
+        idnum: *c_long,
+        serialnum: *c_long,
+        caldata: *[20]c_long,
+    ) c_long;
+
+    pub extern fn CloseAll(local_id: c_long) c_long;
+
+    pub extern fn GetU12Information(
+        handle: *anyopaque,
+        serialnum: *c_long,
+        local_id: *c_long,
+        power: *c_long,
+        cal_data: *[20]c_long,
+        fcdd_max_size: *c_long,
+        hvc_max_size: *c_long,
+    ) c_long;
+
     pub extern fn EAnalogIn(
         idnum: *c_long,
         demo: c_long,
diff --git a/src/main.zig b/src/main.zig
index f72cbc0..ba1928c 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,20 +1,20 @@
 const std = @import("std");
 
-const ljack = @import("./ljacklm.zig");
+const lj = @import("./labjack.zig");
 
 pub fn main() !void {
-    const ver = ljack.getDriverVersion();
+    const ver = lj.getDriverVersion();
     std.debug.print("Driver version: {d}\n", .{ver});
 
-    const device = ljack.Labjack.autodetect();
+    const labjack = lj.Labjack.autodetect();
 
-    const in = try device.analogReadOne(.{ .channel = .diff_01, .gain = 2 });
+    const in = try labjack.analogReadOne(.{ .channel = .diff_01, .gain_index = 2 });
     std.debug.print("Read voltage: {d}. Overvolt: {}\n", .{ in.voltage, in.over_voltage });
-    try device.digitalWriteOne(.{ .channel = .{ .io = 0 }, .level = true });
+    try labjack.digitalWriteOne(.{ .channel = .{ .io = 0 }, .level = true });
 
-    const sample = try device.readAnalogWriteDigital(
+    const sample = try labjack.readAnalogWriteDigital(
         2,
-        .{ .{ .channel = .diff_01, .gain = 2 }, .{ .channel = .diff_23, .gain = 2 } },
+        .{ .{ .channel = .diff_01, .gain_index = 2 }, .{ .channel = .diff_23, .gain_index = 2 } },
         .{false} ** 4,
         true,
     );