controller: implement elevation mask

There's not really any analogous concept for azimuth. This is for a
specific piece of hardware, so there's no real point in making it more
generic. This is respected at the 180 degree point as well, for
software that can handle flipped rotation configurations.

This doesn't currently play well with the elevation offset setting,
which should be applied after this clamping operation. Either this
needs to be moved to the API layer or (more appropriately) the input
range validation needs to move in the controller.

src/Config.zig

@@ -32,11 +32,20 @@ pub fn destroy(allocator: std.mem.Allocator) void {
 
 rotctl: RotControlConfig = .{
     .listen_address = "127.0.0.1",
-    .listen_port = 5432,
+    .listen_port = 4533,
 },
 labjack: LabjackConfig = .{
     .device = .autodetect,
     .feedback_calibration = .{
+        // NOTE: these min and max angles are treated as hardware limits. This serves
+        //       two purposes: first, it means that feedback is always interpolated,
+        //       never extrapolated (though with a two point calibration, that doesn't
+        //       matter much). Second, it prevents having a redundant set of bounds
+        //       values that could potentially desync from these and cause problems.
+        //
+        // The functional min and max are these plus the angle offset values. For
+        // example, given controller.angle_offset.azimuth = -6, the practical minimum
+        // azimuth would be -6 deg and the practical maximum would be 444 deg.
         .azimuth = .{
             .minimum = .{ .voltage = 0.0, .angle = 0.0 },
             .maximum = .{ .voltage = 5.0, .angle = 450.0 },
@@ -48,14 +57,17 @@ labjack: LabjackConfig = .{
     },
 },
 controller: ControllerConfig = .{
-    .azimuth_input = .{ .channel = .diff_01, .gain_index = 2 },
+    .azimuth_input = .{ .channel = .diff_01, .range = .@"5 V" },
-    .elevation_input = .{ .channel = .diff_23, .gain_index = 2 },
+    .elevation_input = .{ .channel = .diff_23, .range = .@"5 V" },
     .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 },
     .angle_offset = .{ .azimuth = 0, .elevation = 0 },
+    // this is a symmetric mask, so the minimum usable elevation is elevation_mask deg
+    // and the maximum usable elevation is 180 - elevation_mask deg
+    .elevation_mask = 0.0,
 },
 
 pub const VoltAngle = struct { voltage: f64, angle: f64 };
@@ -106,6 +118,7 @@ const ControllerConfig = struct {
     parking_posture: AzEl,
     angle_tolerance: AzEl,
     angle_offset: AzEl,
+    elevation_mask: f64,
 
     const OutPair = struct {
         increase: lj.DigitalOutputChannel,

src/LabjackYaesu.zig

@@ -40,7 +40,13 @@ pub fn setTarget(self: LabjackYaesu, target: AzEl) void {
     defer self.lock.unlock();
 
     const controller = @constCast(self.controller);
-    controller.target = target;
+    controller.target = .{
+        .azimuth = target.azimuth,
+        .elevation = @min(
+            @max(target.elevation, config.controller.elevation_mask),
+            180.0 - config.controller.elevation_mask,
+        ),
+    };
     controller.requested_state = .running;
 }
 

src/RotCtl.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 
-const config = @import("./Config.zig").global;
+const Config = @import("./Config.zig");
+const config = Config.global;
 const LabjackYaesu = @import("./LabjackYaesu.zig");
 
 const RotCtl = @This();
@@ -113,6 +114,27 @@ fn getPosition(self: *RotCtl, _: []const u8, tokens: *TokenIter) CommandError!vo
     self.printReply("{d:.1}\n{d:.1}", .{ pos.azimuth, pos.elevation }) catch return error.BadOutput;
 }
 
+fn inRange(request: f64, comptime dof: enum { azimuth, elevation }) bool {
+    return switch (dof) {
+        // zig fmt: off
+        .azimuth => request >= (
+                  config.labjack.feedback_calibration.azimuth.minimum.angle
+                + config.controller.angle_offset.azimuth
+            ) and request <= (
+                  config.labjack.feedback_calibration.azimuth.maximum.angle
+                + config.controller.angle_offset.azimuth
+        ),
+        .elevation => request >= (
+                  config.labjack.feedback_calibration.elevation.minimum.angle
+                + config.controller.angle_offset.elevation
+            ) and request <= (
+                  config.labjack.feedback_calibration.elevation.maximum.angle
+                + config.controller.angle_offset.elevation
+        ),
+        // zig fmt: on
+    };
+}
+
 fn setPosition(self: *RotCtl, _: []const u8, tokens: *TokenIter) CommandError!void {
     const azimuth = std.fmt.parseFloat(f64, tokens.next() orelse {
         return self.replyStatus(.invalid_parameter) catch error.BadOutput;
@@ -120,12 +142,18 @@ fn setPosition(self: *RotCtl, _: []const u8, tokens: *TokenIter) CommandError!vo
         return self.replyStatus(.invalid_parameter) catch error.BadOutput;
     };
 
+    if (!inRange(azimuth, .azimuth))
+        return self.replyStatus(.invalid_parameter) catch error.BadOutput;
+
     const elevation = std.fmt.parseFloat(f64, tokens.next() orelse {
         return self.replyStatus(.invalid_parameter) catch error.BadOutput;
     }) catch {
         return self.replyStatus(.invalid_parameter) catch error.BadOutput;
     };
 
+    if (!inRange(elevation, .elevation))
+        return self.replyStatus(.invalid_parameter) catch error.BadOutput;
+
     self.rotator.setTarget(.{ .azimuth = azimuth, .elevation = elevation });
     return self.replyStatus(.okay) catch error.BadOutput;
 }

src/labjack.zig

@@ -50,7 +50,7 @@ pub const Labjack = struct {
             &id,
             @intFromBool(self.demo),
             input.channelNumber(),
-            input.gain_index,
+            input.gainIndex(),
             &over_v,
             &res.voltage,
         );
@@ -93,7 +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_index;
+            gain.* = from.gainIndex();
         }
         var v_out: [4]f32 = .{0} ** 4;
         var over_v: c_long = 0;
@@ -133,11 +133,15 @@ pub const Labjack = struct {
 
 pub const AnalogInput = struct {
     channel: AnalogInputChannel,
-    gain_index: GainIndex = 0,
+    range: InputRange = .@"20 V",
 
     pub fn channelNumber(self: AnalogInput) u4 {
         return @intFromEnum(self.channel);
     }
+
+    pub fn gainIndex(self: AnalogInput) GainIndex {
+        return @intFromEnum(self.range);
+    }
 };
 
 pub const AnalogReadResult = struct {
@@ -207,6 +211,17 @@ pub const DigitalOutputChannel = union(enum) {
 // 7 => G=20 ±1 volt
 pub const GainIndex = u3;
 
+pub const InputRange = enum(GainIndex) {
+    @"20 V" = 0,
+    @"10 V" = 1,
+    @"5 V" = 2,
+    @"4 V" = 3,
+    @"2.5 V" = 4,
+    @"2 V" = 5,
+    @"1.25 V" = 6,
+    @"1 V" = 7,
+};
+
 pub const PackedOutput = packed struct(u4) {
     io0: bool,
     io1: bool,