Initialising an array

Mightor

Hey there,

I'm looking to use an array to hold servo speed data. Is there a way to initialise it C style, e.g. something like this:

right_servo[noparse]/noparse = { 790, 715, 820, 680, 850, 650}
left_servo[noparse]/noparse = { 713, 790, 687, 817, 667, 829 }

I am aware of the DATA directive, but I'm keen to use an array for fast lookup purposes, I've found the EEPROM to be quite slow and that won't leave me with a lot of time to do more important things, like checking my sensors, etc.

Gr,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Bruce Bates

Mightor -

I know nothing about C, so is this fixed or variable data? In other words, will it be changed during the course of program execution?

I don't know what sort of algorithm you are using to access the EEPROM tables, but that can have as much, or more, to do with the access speed as anything else.

Rgards,

Bruce Bates

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Phil Pilgrim (PhiPi)

If the values are constants and you use the array only one place in your program, you can use LOOKUP as a combination array constructor and indexer. If they're constants, but you want them in a variable array, you can define them in a DATA statement and READ them using a FOR...NEXT loop. Otherwise, you can just READ from EEPROM on a as-needed basis.

PBASIC doesn't have any other array constructors.

-Phil

Mightor

Bruce,

Bruce Bates said...

I know nothing about C, so is this fixed or variable data? In other words, will it be changed during the course of program execution?

I don't know what sort of algorithm you are using to access the EEPROM tables, but that can have as much, or more, to do with the access speed as anything else.

The data will not change. As for EEPROM speed, I found that with one of my previous projects that writing more than two words to the EEPROM would seriously bog down the servos. Does the same not also apply to reading or is this much faster?

I am looking to read the data a bit like this (not necessarily working code):

servo_right DATA Word 790, Word 715, Word 850, Word 650
servo_left  DATA Word 713, Word 790, Word 667, Word 829

FWD            CON      0
FFWD           CON      2
BAK            CON      1
FBAK           CON      3

MotorR         PIN      12
MotorL         PIN      13

SpeedR         VAR      Word
SpeedL         VAR      Word

' Make the bot go forward:
READ servo_right + FWD, SpeedR
READ servo_left + FWD, SpeedL

PULSOUT MotorL, SpeedR
PULSOUT MotorR, SpeedL

' Make the bot go backwards very quickly:
READ servo_right + FBAK, SpeedR
READ servo_left + FBAK, SpeedL

PULSOUT MotorL, SpeedR
PULSOUT MotorR, SpeedL

This seems a lot more code than for example something like this (this is not working code, of course):

right_servo[noparse][[/noparse]] = { 790, 715, 850, 650}
left_servo[noparse][[/noparse]] = { 713, 790, 667, 829 }

FWD            CON      0
FFWD           CON      2
BAK            CON      1
FBAK           CON      3

MotorR         PIN      12
MotorL         PIN      13

' Make the bot go forward:

PULSOUT MotorL, right_servo[noparse][[/noparse]FWD]
PULSOUT MotorR, left_servo[noparse][[/noparse]FWD]

' Make the bot go backwards very quickly:

PULSOUT MotorL, right_servo[noparse][[/noparse]FBAK]
PULSOUT MotorR, left_servo[noparse][[/noparse]FBAK]

That way just looks cleaner and would be a lot faster; there is no EEPROM access and a lot less code. I suppose I could initialise the values in those arrays by one by one, but if there is a way around that, that'd be great [noparse]:)[/noparse]

Gr,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Mightor

Phil,

Phil Pilgrim (PhiPi) said...
If the values are constants and you use the array only one place in your program, you can use LOOKUP as a combination array constructor and indexer.

I see what you mean. I could indeed use the LOOKUP method wrapped in the servo control sub routine. I like that better than the EEPROM way. Thanks for the tip [noparse]:)[/noparse]

Gr,
Mightor

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| What the world needs is more geniuses with humility, there are so few of us left.

Mightor

The code would end up looking a bit like this:

FWD            CON      0
FFWD           CON      2
BAK            CON      1
FBAK           CON      3

MotorR         PIN      12
MotorL         PIN      13

speed          VAR      Word
speedR         VAR      Word
speedL         VAR      Word

' Make the bot go forward one pulse:

speed = FWD : GOSUB Do_Move

' Make the bot go backwards one pulse, very quickly:
speed = FBAK : GOSUB Do_Move

END

Do_Move:
  LOOKUP speed, (790, 715, 850, 650), speedR
  LOOKUP speed, (713, 790, 667, 829), speedL
  PULSOUT MotorL, SpeedL
  PULSOUT MotorR, SpeedR
  return

Gr,
Mightor

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
| What the world needs is more geniuses with humility, there are so few of us left.

Bruce Bates

Mightor -

Reading from a EEPROM is MUCH faster than writing to it.

Regards,

Bruce Bates

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