uM-fpu confusion

Comments

• camt Posts: 45

  2004-10-20 22:35 edited 2004-10-20 22:35

  Hi Tom,
  I assume the numbers you are trying to convert are from a serial source of some kind, and are the left side and right side of a floating point string. To convert to floating point you need to convert the right side to a fraction, then add it to the left side. Alternatively, the uM-FPU can convert an ASCII string directly. Three examples are provided that should solve your problem. Example 1 is the original method you asked about, Examples 2 and 3 use strings.
  -Cam
  
  '

  ---

  ' Example 1
  ' If the integer and fraction part of a number are converted by SERIN
  ' and stored as seperate numbers (as in the original question),
  ' the device must send a fixed number of digits on the right
  ' side of the decimal point for this method to work. In other words,
  ' the device must send trailing zeroes (e.g. 123.5000, 123.0500, 123.0050).
  ' If the device truncates zeroes (e.g. 123.5, 123.05, 123.005), the SERIN
  ' format conversion will yield 5 for the right side in all cases,
  ' since leading zeroes are ignored by SERIN. If the format has 4 digits
  ' to the right of the decimal point, the following code will convert the
  ' number and store it in register 1 on the uM-FPU.
  '

  ---

  
  val VAR Word(2)
  
  SERIN 0, 16884, [noparse][[/noparse]DEC val(0), SKIP 1, DEC val(1)] 'read left/right values
  
  fA = 1 'select uM-FPU register 1
  fLow = val(1) 'load number from right side to uM-FPU
  GOSUB Load_FloatWord 'convert to floating point
  GOSUB Fset
  fLow = 10000 'load 10000
  GOSUB Load_FloatWord 'convert to floating point
  GOSUB Fdivide 'divide right side by 10000 to get fraction
  fLow = val(0) 'load number from left side to uM-FPU
  GOSUB Load_FloatWord 'convert to floating point
  GOSUB Fadd 'add to fraction
  '...
  
  '

  ---

  ' Example 2
  ' This example reads the string (e.g. 2628.8133) directly from the serial
  ' port and sends it to the uM-FPU for conversion. It terminates the
  ' conversion when a comma is read from the serial port. This example
  ' conserves variable space since no extra variables are required.
  '

  ---

  
  GOSUB Load_SerialString 'load
  fA = 1
  GOSUB Fset
  '...
  
  Load_SerialString:
  fOpcode = $F9 'convert ASCII to float
  GOSUB Sys_Command
  DO
  SERIN 0, 16884, [noparse][[/noparse]fChar] 'read character from serial port
  IF fChar = "," THEN EXIT 'check for comma terminator
  SHIFTOUT FpuData, FpuClock, MSBFIRST, [noparse][[/noparse]fChar] ' send character to FPU
  LOOP
  SHIFTOUT FpuData, FpuClock, MSBFIRST, [noparse][[/noparse]0] ' send zero terminator
  RETURN
  
  '

  ---

  ' Example 3
  ' This example reads the string into RAM, then sends it to the uM-FPU for
  ' conversion. It requires a 10 character string buffer.
  '

  ---

  
  serStr VAR Byte(10)
  cnt VAR Byte
  
  SERIN 0, 16884, [noparse][[/noparse]STR serStr\10\","] 'read string
  GOSUB Load_RamString
  fA = 1
  '...
  
  Load_RamString:
  fOpcode = $F9 'convert ASCII to float
  GOSUB Sys_Command
  FOR cnt = 0 TO 10
  IF serStr(cnt) = 0 THEN EXIT 'check for comma terminator
  SHIFTOUT FpuData, FpuClock, MSBFIRST, [noparse][[/noparse]serStr(cnt)] ' send character to FPU
  NEXT
  SHIFTOUT FpuData, FpuClock, MSBFIRST, [noparse][[/noparse]0] ' send zero terminator
  RETURN