模拟摇杆调制轮无响应求助：仅弯音轮功能正常

我编写了一段脚本，意图让模拟摇杆的垂直轴模拟MIDI调制轮，水平轴模拟弯音轮，但测试时仅弯音轮功能正常，调制轮完全无反应。已尝试更换不同轴，问题依旧。

脚本代码 #

// buttons (bitmask), numbuttons (valid bits in buttons)
// systime (time in seconds)
// axis(x), numaxis (number actually supported)
// pov(x), numpov, pov(x) > 360 if not pointing

// event(msg1,msg2,msg3) to send events

// settings
joystick_modwheel_axis = 2; 
joystick_pitchblend_axis = 1; 
midi_channel  = 0; // 0-15
modwheel_cc   = 1; // 0-127
pitchblend_cc = 2; // 0-127

modwheel_val = floor(abs(axis(joystick_modwheel_axis) * 127));
pitchblend_val = floor((axis(joystick_pitchblend_axis) * 8192) + 8192);

modwheel_val != modwheel_val_old ? (
  event($xb0 | midi_channel, modwheel_cc, modwheel_val);
  modwheel_val_old = modwheel_val;
);

pitchblend_val != pitchblend_val_old ? (
  event($xe0 | midi_channel, pitchblend_val & 0x7F, pitchblend_val >> 7);
  pitchblend_val_old = pitchblend_val;
);

功能示意图 #

问题排查与修复方案 #

1. 未初始化状态变量

代码中modwheel_val_old和pitchblend_val_old没有初始值，第一次执行时，modwheel_val != modwheel_val_old的判断会因modwheel_val_old未定义而失效，导致调制轮事件无法触发，后续状态更新也会异常。

修复： 在脚本开头添加变量初始化：

modwheel_val_old = -1;
pitchblend_val_old = -1;

2. 轴索引与值范围验证

• 确认axis(x)的索引规则：部分平台轴索引从0开始，joystick_modwheel_axis = 2可能指向不存在的轴。可添加调试代码输出轴值：

  print("Mod Wheel Axis Value: " .. axis(joystick_modwheel_axis));
  

• 原代码用abs()处理轴值，会丢失摇杆的方向信息（垂直轴通常是-1到1，对应调制轮0-127的范围），更合理的映射应该是把-1→0，0→64，1→127：

  modwheel_val = floor((axis(joystick_modwheel_axis) * 63.5) + 63.5);
  // 限制值在0-127之间
  modwheel_val = math.max(0, math.min(127, modwheel_val));
  

3. 脚本执行逻辑确认

确保脚本设置为持续运行，而非仅在按键触发时执行——部分平台默认只在输入事件（如按键按下）时运行脚本，摇杆轴的平滑变化可能无法触发脚本执行。

完整修复后的脚本 #

// buttons (bitmask), numbuttons (valid bits in buttons)
// systime (time in seconds)
// axis(x), numaxis (number actually supported)
// pov(x), numpov, pov(x) > 360 if not pointing

// event(msg1,msg2,msg3) to send events

// 初始化状态变量，确保首次判断生效
modwheel_val_old = -1;
pitchblend_val_old = -1;

// settings
joystick_modwheel_axis = 2; 
joystick_pitchblend_axis = 1; 
midi_channel  = 0; // 0-15
modwheel_cc   = 1; // 0-127
pitchblend_cc = 2; // 0-127

// 调制轮值映射：摇杆-1~1 → MIDI 0~127（中心64）
modwheel_val = floor((axis(joystick_modwheel_axis) * 63.5) + 63.5);
modwheel_val = math.max(0, math.min(127, modwheel_val));

// 弯音轮值映射：摇杆-1~1 → MIDI 0~16383
pitchblend_val = floor((axis(joystick_pitchblend_axis) * 8192) + 8192);
pitchblend_val = math.max(0, math.min(16383, pitchblend_val));

// 发送调制轮控制变更事件
if modwheel_val != modwheel_val_old then
  event($xb0 | midi_channel, modwheel_cc, modwheel_val);
  modwheel_val_old = modwheel_val;
end

// 发送弯音轮事件
if pitchblend_val != pitchblend_val_old then
  event($xe0 | midi_channel, pitchblend_val & 0x7F, pitchblend_val >> 7);
  pitchblend_val_old = pitchblend_val;
end

内容的提问来源于stack exchange，提问作者Peter Tremblay