Serial Encoding with Print
- Confluence
- Topic Author
7 years 11 months ago #29530470
by Confluence
Serial Encoding with Print was created by Confluence
Just posting this in case others need similar functionality.
For our particular use case, we needed the encoder counts to be sent from our FDC32XX controller at 50 Hz. The print command currently can only print string outputs. Since the encoders are int32's they are bounded by +- ~2 billion. Printing three of these values over a serial line is very slow and not efficent (2 billion is 10 chars, + 1 for negative sign, so possibly 33 characters, not counting headers or delimiters).
Our soultion uses byte encoding to represent each byte of a number as an ASCII char and sent over the serial port. The biggest issue is that the current print command can not print variables as ASCII chars. So the attached code masks each byte to get the value of each bit and then does 8 if/then/else comparisons to print the correct ASCII symbol. Using this solution we are able to encode numbers into compact byte values for serial communication.
For our particular use case, we needed the encoder counts to be sent from our FDC32XX controller at 50 Hz. The print command currently can only print string outputs. Since the encoders are int32's they are bounded by +- ~2 billion. Printing three of these values over a serial line is very slow and not efficent (2 billion is 10 chars, + 1 for negative sign, so possibly 33 characters, not counting headers or delimiters).
Our soultion uses byte encoding to represent each byte of a number as an ASCII char and sent over the serial port. The biggest issue is that the current print command can not print variables as ASCII chars. So the attached code masks each byte to get the value of each bit and then does 8 if/then/else comparisons to print the correct ASCII symbol. Using this solution we are able to encode numbers into compact byte values for serial communication.
' Encoder Packet Printer
' Packet format:
' [1:3] Az: header (uint8)x3
' [4:5] enc1 encoder1 (uint16)
' [6:7] enc2 encoder2 (uint16)
' [8:9] enc3 encoder3 (uint16)
' [10] csum checksum byte (uint8) (sum of encoders mod 256)
' << init >>
wait(500) ' pause before script execution
' << main loop >>
while 1
enc1 = getvalue(_ABCNTR, 1) ' get encoder values
enc2 = getvalue(_ABCNTR, 2)
enc3 = getvalue(_ABCNTR, 3)
gosub encmod ' bound encoder values to less than 2-byte values
gosub serialize ' split into single byte chunks
gosub chksum ' calculate checksum
gosub packetprinter ' print 10-byte packet over serial
end while
' << bound encoder counts to [0,64000] >>
encmod:
val1 = enc1 mod 64000 ' encoder values are +/-2,000,000,000
val2 = enc2 mod 64000 ' 64000 is the largest 2-byte value
val3 = enc3 mod 64000 ' to cleanly mod with 2,000,000,000
return
' << serialize 2 byte values (~uint16) into 1 byte chunks >>
serialize:
' encoder 1
byte1 = (val1 and 0b1111111100000000) >> 8 ' mask, shift
byte2 = (val1 and 0b0000000011111111) ' mask
' encoder 2
byte3 = (val2 and 0b1111111100000000) >> 8
byte4 = (val2 and 0b0000000011111111)
' encoder 3
byte5 = (val2 and 0b1111111100000000) >> 8
byte6 = (val3 and 0b0000000011111111)
return
' << calculate checksum byte >>
chksum:
csum = (byte1 + byte2 + byte3 + byte4 + byte5 + byte6) mod 256
return
' << output packet over serial >>
packetprinter:
print("Az4") ' [1:3] header (uint8)x3
val = byte1 ' [4:5] enc1 (uint16)
gosub twiddlebit
val = byte2
gosub twiddlebit
val = byte3 ' [6:7] enc2 (uint16)
gosub twiddlebit
val = byte4
gosub twiddlebit
val = byte5 ' [8:9] enc3 (uint16)
gosub twiddlebit
val = byte6
gosub twiddlebit
val = csum ' [10] checksum (uint8)
gosub twiddlebit
return
' << print val as uint8 char via serial >>
twiddlebit: ' convert to binary for minimum/consistent runtime
bit1 = (val and 0b00000001) ' LSB
if (val and 0b00000010)>0 then bit2=1 else bit2=0
if (val and 0b00000100)>0 then bit3=1 else bit3=0 ' Speedfix: changed division to comparison
if (val and 0b00001000)>0 then bit4=1 else bit4=0
if (val and 0b00010000)>0 then bit5=1 else bit5=0
if (val and 0b00100000)>0 then bit6=1 else bit6=0
if (val and 0b01000000)>0 then bit7=1 else bit7=0
if (val and 0b10000000)>0 then bit8=1 else bit8=0 ' MSB
if bit8 then ' begin /binary/ tree
if bit7 then
if bit6 then
if bit5 then
if bit4 then 'byte value
if bit3 then
if bit2 then
if bit1 then
print("\x0FF") '255
else
print("\x0FE") '254
end if
else
if bit1 then
print("\x0FD") '253
else
print("\x0FC") '252
end if
end if
else
if bit2 then
if bit1 then
print("\x0FB") '251
else
print("\x0FA") '250
end if
else
if bit1 then
print("\x0F9") '249
else
print("\x0F8") '248
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x0F7") '247
else
print("\x0F6") '246
end if
else
if bit1 then
print("\x0F5") '245
else
print("\x0F4") '244
end if
end if
else
if bit2 then
if bit1 then
print("\x0F3") '243
else
print("\x0F2") '242
end if
else
if bit1 then
print("\x0F1") '241
else
print("\x0F0") '240
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x0EF") '239
else
print("\x0EE") '238
end if
else
if bit1 then
print("\x0ED") '237
else
print("\x0EC") '236
end if
end if
else
if bit2 then
if bit1 then
print("\x0EB") '235
else
print("\x0EA") '234
end if
else
if bit1 then
print("\x0E9") '232
else
print("\x0E8") '231
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x0E7") '230
else
print("\x0E6") '229
end if
else
if bit1 then
print("\x0E5") '228
else
print("\x0E4") '227
end if
end if
else
if bit2 then
if bit1 then
print("\x0E3") '226
else
print("\x0E2") '225
end if
else
if bit1 then
print("\x0E1") '224
else
print("\x0E0") '223
end if
end if
end if
end if
end if
else
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x0DF") '222
else
print("\x0DE") '221
end if
else
if bit1 then
print("\x0DD") '220
else
print("\x0DC") '219
end if
end if
else
if bit2 then
if bit1 then
print("\x0DB") '218
else
print("\x0DA") '217
end if
else
if bit1 then
print("\x0D9") '216
else
print("\x0D8") '215
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x0D7") '214
else
print("\x0D6") '213
end if
else
if bit1 then
print("\x0D5") '212
else
print("\x0D4") '211
end if
end if
else
if bit2 then
if bit1 then
print("\x0D3") '210
else
print("\x0D2") '209
end if
else
if bit1 then
print("\x0D1") '208
else
print("\x0D0") '207
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x0CF") '206
else
print("\x0CE") '205
end if
else
if bit1 then
print("\x0CD") '204
else
print("\x0CC") '203
end if
end if
else
if bit2 then
if bit1 then
print("\x0CB") '202
else
print("\x0CA") '201
end if
else
if bit1 then
print("\x0C9") '200
else
print("\x0C8") '199
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x0C7") '198
else
print("\x0C6") '197
end if
else
if bit1 then
print("\x0C5") '196
else
print("\x0C4") '195
end if
end if
else
if bit2 then
if bit1 then
print("\x0C3") '194
else
print("\x0C2") '193
end if
else
if bit1 then
print("\x0C1") '192
else
print("\x0C0") '191
end if
end if
end if
end if
end if
end if
else
if bit6 then
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x0BF") '190
else
print("\x0BE") '189
end if
else
if bit1 then
print("\x0BD") '188
else
print("\x0BC") '187
end if
end if
else
if bit2 then
if bit1 then
print("\x0BB") '186
else
print("\x0BA") '185
end if
else
if bit1 then
print("\x0B9") '184
else
print("\x0B8") '183
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x0B7") '182
else
print("\x0B6") '181
end if
else
if bit1 then
print("\x0B5") '180
else
print("\x0B4") '179
end if
end if
else
if bit2 then
if bit1 then
print("\x0B3") '178
else
print("\x0B2") '177
end if
else
if bit1 then
print("\x0B1") '176
else
print("\x0B0") '175
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x0AF") '174
else
print("\x0AE") '173
end if
else
if bit1 then
print("\x0AD") '172
else
print("\x0AC") '171
end if
end if
else
if bit2 then
if bit1 then
print("\x0AB") '170
else
print("\x0AA") '169
end if
else
if bit1 then
print("\x0A9") '168
else
print("\x0A8") '167
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x0A7") '166
else
print("\x0A6") '165
end if
else
if bit1 then
print("\x0A5") '164
else
print("\x0A4") '163
end if
end if
else
if bit2 then
if bit1 then
print("\x0A3") '162
else
print("\x0A2") '161
end if
else
if bit1 then
print("\x0A1") '160
else
print("\x0A0") '159
end if
end if
end if
end if
end if
else
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x09F") '158
else
print("\x09E") '157
end if
else
if bit1 then
print("\x09D") '156
else
print("\x09C") '155
end if
end if
else
if bit2 then
if bit1 then
print("\x09B") '154
else
print("\x09A") '153
end if
else
if bit1 then
print("\x099") '152
else
print("\x098") '151
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x097") '150
else
print("\x096") '149
end if
else
if bit1 then
print("\x095") '148
else
print("\x094") '147
end if
end if
else
if bit2 then
if bit1 then
print("\x093") '146
else
print("\x092") '145
end if
else
if bit1 then
print("\x091") '144
else
print("\x090") '143
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x08F") '142
else
print("\x08E") '141
end if
else
if bit1 then
print("\x08D") '140
else
print("\x08C") '139
end if
end if
else
if bit2 then
if bit1 then
print("\x08B") '138
else
print("\x08A") '137
end if
else
if bit1 then
print("\x089") '136
else
print("\x088") '135
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x087") '134
else
print("\x086") '133
end if
else
if bit1 then
print("\x085") '132
else
print("\x084") '131
end if
end if
else
if bit2 then
if bit1 then
print("\x083") '130
else
print("\x082") '129
end if
else
if bit1 then
print("\x081") '128
else
print("\x080") '128
end if
end if
end if
end if
end if
end if
end if
else
if bit7 then
if bit6 then
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x07F") '127
else
print("\x07E") '126
end if
else
if bit1 then
print("\x07D") '125
else
print("\x07C") '124
end if
end if
else
if bit2 then
if bit1 then
print("\x07B") '123
else
print("\x07A") '122
end if
else
if bit1 then
print("\x079") '121
else
print("\x078") '120
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x077") '119
else
print("\x076") '118
end if
else
if bit1 then
print("\x075") '117
else
print("\x074") '116
end if
end if
else
if bit2 then
if bit1 then
print("\x073") '115
else
print("\x072") '114
end if
else
if bit1 then
print("\x071") '113
else
print("\x070") '112
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x06F") '111
else
print("\x06E") '110
end if
else
if bit1 then
print("\x06D") '109
else
print("\x06C") '108
end if
end if
else
if bit2 then
if bit1 then
print("\x06B") '107
else
print("\x06A") '106
end if
else
if bit1 then
print("\x069") '105
else
print("\x068") '104
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x067") '103
else
print("\x066") '102
end if
else
if bit1 then
print("\x065") '101
else
print("\x064") '100
end if
end if
else
if bit2 then
if bit1 then
print("\x063") ' 99
else
print("\x062") ' 98
end if
else
if bit1 then
print("\x061") ' 97
else
print("\x060") ' 96
end if
end if
end if
end if
end if
else
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x05F") ' 95
else
print("\x05E") ' 94
end if
else
if bit1 then
print("\x05D") ' 93
else
print("\x05C") ' 92
end if
end if
else
if bit2 then
if bit1 then
print("\x05B") ' 91
else
print("\x05A") ' 90
end if
else
if bit1 then
print("\x059") ' 89
else
print("\x058") ' 88
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x057") ' 87
else
print("\x056") ' 86
end if
else
if bit1 then
print("\x055") ' 85
else
print("\x054") ' 84
end if
end if
else
if bit2 then
if bit1 then
print("\x053") ' 83
else
print("\x052") ' 82
end if
else
if bit1 then
print("\x051") ' 81
else
print("\x050") ' 80
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x04F") ' 79
else
print("\x04E") ' 78
end if
else
if bit1 then
print("\x04D") ' 77
else
print("\x04C") ' 76
end if
end if
else
if bit2 then
if bit1 then
print("\x04B") ' 75
else
print("\x04A") ' 74
end if
else
if bit1 then
print("\x049") ' 73
else
print("\x048") ' 72
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x047") ' 71
else
print("\x046") ' 70
end if
else
if bit1 then
print("\x045") ' 69
else
print("\x044") ' 68
end if
end if
else
if bit2 then
if bit1 then
print("\x043") ' 67
else
print("\x042") ' 66
end if
else
if bit1 then
print("\x041") ' 65
else
print("\x040") ' 64
end if
end if
end if
end if
end if
end if
else
if bit6 then
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x03F") ' 63
else
print("\x03E") ' 62
end if
else
if bit1 then
print("\x03D") ' 61
else
print("\x03C") ' 60
end if
end if
else
if bit2 then
if bit1 then
print("\x03B") ' 59
else
print("\x03A") ' 58
end if
else
if bit1 then
print("\x039") ' 57
else
print("\x038") ' 56
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x037") ' 55
else
print("\x036") ' 54
end if
else
if bit1 then
print("\x035") ' 53
else
print("\x034") ' 52
end if
end if
else
if bit2 then
if bit1 then
print("\x033") ' 51
else
print("\x032") ' 50
end if
else
if bit1 then
print("\x031") ' 49
else
print("\x030") ' 48
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x02F") ' 47
else
print("\x02E") ' 46
end if
else
if bit1 then
print("\x02D") ' 45
else
print("\x02C") ' 44
end if
end if
else
if bit2 then
if bit1 then
print("\x02B") ' 43
else
print("\x02A") ' 42
end if
else
if bit1 then
print("\x029") ' 41
else
print("\x028") ' 40
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x027") ' 39
else
print("\x026") ' 38
end if
else
if bit1 then
print("\x025") ' 37
else
print("\x024") ' 36
end if
end if
else
if bit2 then
if bit1 then
print("\x023") ' 35
else
print("\x022") ' 34
end if
else
if bit1 then
print("\x021") ' 33
else
print("\x020") ' 32
end if
end if
end if
end if
end if
else
if bit5 then
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x01F") ' 31
else
print("\x01E") ' 30
end if
else
if bit1 then
print("\x01D") ' 29
else
print("\x01C") ' 28
end if
end if
else
if bit2 then
if bit1 then
print("\x01B") ' 27
else
print("\x01A") ' 26
end if
else
if bit1 then
print("\x019") ' 25
else
print("\x018") ' 24
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x017") ' 23
else
print("\x016") ' 22
end if
else
if bit1 then
print("\x015") ' 21
else
print("\x014") ' 20
end if
end if
else
if bit2 then
if bit1 then
print("\x013") ' 19
else
print("\x012") ' 18
end if
else
if bit1 then
print("\x011") ' 17
else
print("\x010") ' 16
end if
end if
end if
end if
else
if bit4 then
if bit3 then
if bit2 then
if bit1 then
print("\x00F") ' 15
else
print("\x00E") ' 14
end if
else
if bit1 then
print("\x00D") ' 13
else
print("\x00C") ' 12
end if
end if
else
if bit2 then
if bit1 then
print("\x00B") ' 11
else
print("\x00A") ' 10
end if
else
if bit1 then
print("\x009") ' 9
else
print("\x008") ' 8
end if
end if
end if
else
if bit3 then
if bit2 then
if bit1 then
print("\x007") ' 7
else
print("\x006") ' 6
end if
else
if bit1 then
print("\x005") ' 5
else
print("\x004") ' 4
end if
end if
else
if bit2 then
if bit1 then
print("\x003") ' 3
else
print("\x002") ' 2
end if
else
if bit1 then
print("\x001") ' 1
else
print("\x000") ' 0
end if
end if
end if
end if
end if
end if
end if
end if
return
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