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Implement UART decoder

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Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
This commit is contained in:
Joey Yakimowich-Payne 2026-08-11 12:23:07 +09:00
commit a7f07c67b8
2 changed files with 385 additions and 0 deletions
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124
switch_uart_protocol.cpp Normal file
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#include "switch_uart_protocol.h"
namespace {
SwitchInputState make_neutral_state() {
SwitchInputState state{};
state.lx = SWITCH_PRO_JOYSTICK_MID;
state.ly = SWITCH_PRO_JOYSTICK_MID;
state.rx = SWITCH_PRO_JOYSTICK_MID;
state.ry = SWITCH_PRO_JOYSTICK_MID;
state.imu_sample_count = 0;
return state;
}
} // namespace
bool switch_uart_decode_input_frame(
const uint8_t* packet,
uint8_t length,
SwitchInputState* out_state) {
if (length < 12) {
return false;
}
if (packet[0] != 0xAA) {
return false;
}
if (packet[1] != 0x02) {
return false;
}
const uint8_t payload_len = packet[2];
if (static_cast<uint16_t>(payload_len) + 4u != length) {
return false;
}
uint16_t sum = 0;
for (uint16_t index = 0; index < static_cast<uint16_t>(3u + payload_len); ++index) {
sum += packet[index];
}
if ((sum & 0xFF) != packet[length - 1]) {
return false;
}
if (payload_len < 8) {
return false;
}
const uint16_t buttons = static_cast<uint16_t>(packet[3]) |
(static_cast<uint16_t>(packet[4]) << 8);
const uint8_t hat = packet[5];
const uint8_t lx = packet[6];
const uint8_t ly = packet[7];
const uint8_t rx = packet[8];
const uint8_t ry = packet[9];
uint8_t imu_count = packet[10];
if (imu_count > 3) {
imu_count = 3;
}
const uint16_t required_payload_len =
static_cast<uint16_t>(8u + static_cast<uint16_t>(imu_count) * 12u);
if (payload_len < required_payload_len) {
return false;
}
const auto expand_axis = [](uint8_t value) -> uint16_t {
return static_cast<uint16_t>(value) << 8 | value;
};
const auto read_int16 = [](const uint8_t* source) -> int16_t {
return static_cast<int16_t>(
static_cast<uint16_t>(source[0]) |
(static_cast<uint16_t>(source[1]) << 8));
};
SwitchInputState state = make_neutral_state();
state.imu_sample_count = imu_count;
for (uint8_t index = 0; index < imu_count; ++index) {
const uint8_t* base = &packet[11 + index * 12];
state.imu_samples[index].accel_x = read_int16(base);
state.imu_samples[index].accel_y = read_int16(base + 2);
state.imu_samples[index].accel_z = read_int16(base + 4);
state.imu_samples[index].gyro_x = read_int16(base + 6);
state.imu_samples[index].gyro_y = read_int16(base + 8);
state.imu_samples[index].gyro_z = read_int16(base + 10);
}
switch (hat) {
case SWITCH_PRO_HAT_UP: state.dpad_up = true; break;
case SWITCH_PRO_HAT_UPRIGHT: state.dpad_up = true; state.dpad_right = true; break;
case SWITCH_PRO_HAT_RIGHT: state.dpad_right = true; break;
case SWITCH_PRO_HAT_DOWNRIGHT: state.dpad_down = true; state.dpad_right = true; break;
case SWITCH_PRO_HAT_DOWN: state.dpad_down = true; break;
case SWITCH_PRO_HAT_DOWNLEFT: state.dpad_down = true; state.dpad_left = true; break;
case SWITCH_PRO_HAT_LEFT: state.dpad_left = true; break;
case SWITCH_PRO_HAT_UPLEFT: state.dpad_up = true; state.dpad_left = true; break;
default: break;
}
state.button_y = buttons & SWITCH_PRO_MASK_Y;
state.button_x = buttons & SWITCH_PRO_MASK_X;
state.button_b = buttons & SWITCH_PRO_MASK_B;
state.button_a = buttons & SWITCH_PRO_MASK_A;
state.button_r = buttons & SWITCH_PRO_MASK_R;
state.button_zr = buttons & SWITCH_PRO_MASK_ZR;
state.button_plus = buttons & SWITCH_PRO_MASK_PLUS;
state.button_minus = buttons & SWITCH_PRO_MASK_MINUS;
state.button_r3 = buttons & SWITCH_PRO_MASK_R3;
state.button_l3 = buttons & SWITCH_PRO_MASK_L3;
state.button_home = buttons & SWITCH_PRO_MASK_HOME;
state.button_capture = buttons & SWITCH_PRO_MASK_CAPTURE;
state.button_zl = buttons & SWITCH_PRO_MASK_ZL;
state.button_l = buttons & SWITCH_PRO_MASK_L;
state.lx = expand_axis(lx);
state.ly = expand_axis(ly);
state.rx = expand_axis(rx);
state.ry = expand_axis(ry);
if (!out_state) {
return false;
}
*out_state = state;
return true;
}