TI 官方例程中对3轴加速计获得数据的处理：低通过滤、防抖算法等

摘取自 eZ430-Chronos CC 1_2.tcl

# ----------------------------------------------------------------------------------------# SimpliciTI acc / ppt -------------------------------------------------------------------# Zero-set x-y-z valuesproc calibrate_sensor {} {  global simpliciti_on  global accel_x accel_y accel_z accel_x_offset accel_y_offset accel_z_offset    # return if SPL is not active    if { $simpliciti_on == 0 } { return }    # Wait until new frame has arrived  after 100    # Clear offset  set accel_x_offset  0  set accel_y_offset  0  set accel_z_offset  0  set accel_x         0  set accel_y         0  set accel_z         0  # get new data  get_spl_data    # set new offset  set accel_x_offset $accel_x  set accel_y_offset $accel_y  set accel_z_offset $accel_z}# Read received SimpliciTI data from RF access pointproc get_spl_data {} {  global w  global simpliciti_on simpliciti_ap_started simpliciti_mode  global accel_x accel_y accel_z accel_x_offset accel_y_offset accel_z_offset  global button_event_text button_event previous_button_event button_timeout      # SimpliciTI off?    if { $simpliciti_on == 0 } { return }  # Update status box    catch { BM_GetStatus } status  # Check RF access point status byte    if { $status == 2 } {      # Trying to link    updateStatusSPL "Starting access point."    return    } elseif { $status == 3 } {        # Read 32-bit SimpliciTI data from dongle    # Data format is [Z-Y-X-KEY]    catch { BM_SPL_GetData } data        # Just started? Ignore first data    if { $simpliciti_ap_started == 0} {      if { $simpliciti_mode == "acc" } {        updateStatusSPL "Access point started. Now start watch in acc or ppt mode."       } else {        updateStatusSPL "Access point started. Now start watch in sync mode."       }      set simpliciti_ap_started 1      return    } else {      # if Byte0 is 0xFF, data has already been read from USB buffer, so do nothing      if { ($data & 0xFF) == 0xFF } { return }     }        # Extract watch button event from SimpliciTi data bits 7:0    set button_event 0        if { [expr ($data & 0xF0) ] != 0 } {            set button_event  [expr ($data & 0xF0) ]            if { $button_event == 0x10 } {        set button_event_text "Button (*)"      } elseif { $button_event == 0x20 } {        set button_event_text "Button (#)"      } elseif { $button_event == 0x30 } {        set button_event_text "Button (Up)"      }      # Watch can send either key events (2) or mouse clicks (1) - distinguish mode here      if { [expr ($data & 0x0F) ] == 0x01 } {        switch $button_event {          16    { catch { BM_SetMouseClick 1 } res                   updateStatusSPL "Left mouse click." }          32    { catch { BM_SetMouseClick 3 } res                  updateStatusSPL "Left mouse doubleclick." }          48    { catch { BM_SetMouseClick 2 } res                   updateStatusSPL "Right mouse click." }        }      } elseif { [expr ($data & 0x0F) ] == 0x02 } {        updateStatusSPL "$button_event_text was pressed."        switch $button_event {          16    { button_set M1 }          32    { button_set M2 }          48    { button_set S1 }        }      }      update      after 500      # Dummy read to clear USB buffer      catch { BM_SPL_GetData } data      after 20      catch { BM_SPL_GetData } data      return    }        # Keep on drawing X-Y-Z values        # Keep previous values for low pass filtering    set prev_x  $accel_x    set prev_y  $accel_y    set prev_z  $accel_z        # Extract acceleration values from upper data bits    set accel_x [expr (($data >> 8)  & 0xFF)]    set accel_y [expr (($data >> 16) & 0xFF)]    set accel_z [expr (($data >> 24) & 0xFF)]        # Convert raw data to signed integer        # Get sign (1=minus, 0=plus)    set sign_x  [expr ($accel_x&0x80) >> 7]    set sign_y  [expr ($accel_y&0x80) >> 7]    set sign_z  [expr ($accel_z&0x80) >> 7]        # Convert negative 2's complement number to signed decimal    if { $sign_x == 1 } {       set accel_x [ expr (((~$accel_x) & 0xFF ) + 1)*(-1) ]    }        if { $sign_y == 1 } {       set accel_y [ expr (((~$accel_y) & 0xFF ) + 1)*(-1) ]    }        if { $sign_z == 1 } {       set accel_z [ expr (((~$accel_z) & 0xFF ) + 1)*(-1) ]    }            # Low pass filter values from acceleration sensor to avoid jitter    set accel_x [expr ($accel_x*18*0.5) + $prev_x*0.5 - $accel_x_offset]    set accel_y [expr ($accel_y*18*0.5) + $prev_y*0.5 - $accel_y_offset]    set accel_z [expr ($accel_z*18*0.5) + $prev_z*0.5 - $accel_z_offset]      # Display values in status line    updateStatusSPL "Receiving data from acceleration sensor  X=[format %4.0f $accel_x]  Y=[format %4.0f $accel_y]  Z=[format %4.0f $accel_z]"        # Use values to move mouse cursor     move_cursor    # Update wave graphs    add_wave_coords  }}