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Fix NeuroPawn Knight EEG scale factor (#9) #867

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Merged
Andrey1994 merged 1 commit into from
Oct 21, 2026
Merged

Fix NeuroPawn Knight EEG scale factor (#9) #867

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2 changes: 2 additions & 0 deletions src/board_controller/neuropawn/inc/knight_base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,4 +39,6 @@ class KnightBase : public Board

static constexpr int start_byte = 0xA0;
static constexpr int end_byte = 0xC0;
// 4 Vref / (2^15 - 1) / gain / 79.57 * 1e6 -> uV. Gain is fixed at 12.
static constexpr double eeg_scale = 4.0 / (32768.0 - 1.0) / 12.0 / 79.57 * 1000000.0;
};
6 changes: 2 additions & 4 deletions src/board_controller/neuropawn/knight.cpp
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@
#include <math.h>
#include <vector>

#include "custom_cast.h"
Expand Down Expand Up @@ -29,7 +28,6 @@ void Knight::read_thread ()

int res;
unsigned char b[20] = {0};
float eeg_scale = 4 / float ((pow (2, 15) - 1)) / 12 * 1000000.;
int num_rows = board_descr["default"]["num_rows"];
double *package = new double[num_rows];
for (int i = 0; i < num_rows; i++)
Expand Down Expand Up @@ -81,8 +79,8 @@ void Knight::read_thread ()
// exg data retrieval
for (unsigned int i = 0; i < eeg_channels.size (); i++)
{
package[eeg_channels[i]] =
eeg_scale * cast_16bit_to_int32 (b + 1 + 2 * i); // CHANGE TO 2+2*i if not working
package[eeg_channels[i]] = KnightBase::eeg_scale *
cast_16bit_to_int32 (b + 1 + 2 * i); // CHANGE TO 2+2*i if not working
}

// other channel data retrieval
Expand Down
1 change: 1 addition & 0 deletions src/board_controller/neuropawn/knight_base.cpp
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Expand Up @@ -12,6 +12,7 @@ using json = nlohmann::json;

constexpr int KnightBase::start_byte;
constexpr int KnightBase::end_byte;
constexpr double KnightBase::eeg_scale;

KnightBase::KnightBase (int board_id, struct BrainFlowInputParams params) : Board (board_id, params)
{
Expand Down
5 changes: 2 additions & 3 deletions src/board_controller/neuropawn/knight_imu.cpp
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
#include <cstdint>
#include <cstring>
#include <limits>
#include <math.h>
#include <vector>

#include "custom_cast.h"
Expand Down Expand Up @@ -35,7 +34,6 @@ void KnightIMU::read_thread ()

unsigned char b[frame_payload_size] = {0};

float eeg_scale = 4 / float ((pow (2, 15) - 1)) / 12 * 1000000.;
int num_rows = board_descr["default"]["num_rows"];
double *package = new double[num_rows];
for (int i = 0; i < num_rows; i++)
Expand Down Expand Up @@ -91,7 +89,8 @@ void KnightIMU::read_thread ()
const int exg_offset = 1;
for (unsigned int i = 0; i < eeg_channels.size () && i < exg_channels_count; i++)
{
package[eeg_channels[i]] = eeg_scale * cast_16bit_to_int32 (b + exg_offset + 2 * i);
package[eeg_channels[i]] =
KnightBase::eeg_scale * cast_16bit_to_int32 (b + exg_offset + 2 * i);
}

// other channel data retrieval (keep old behavior)
Expand Down
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