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TSEYFARTH
Joined: 01 Jul 2006
Posts: 1054
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 Posted: Tue Jul 29, 2014 5:16 am Post subject: Const - how to Create a Const and set a default value? |
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Hello all,
I want to set a constant as:
Const CommandDoSomething = &H02
But, in addition, I want to set the CommandDoSomething (&H02) with a default Value of &HD4
Is this possible with an Alias? Is this possible at all? Anyone how to do it??
This is what I am trying to emulate:
Properties:
Number Name Default Summary
0x0002 GLOBAL_LOW_BATT_THRESH 0x18 Low battery threshold
Where the GLOBAL_LOW_BATT_THRESH is a Const = &H2; and the default value of this property is &H18.
Thanks all,
Tim
(BASCOM-AVR version : 2.0.7.7 ) |
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six1
Joined: 27 Feb 2009
Posts: 553
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| Posted: Tue Jul 29, 2014 6:39 am Post subject: |
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Hi Tim,
it's not realy clear to me...
A Constant is a non editable constant value. You will define it in Sourcecode and this is, what it is... uneditable.
If you define
Const CommandDoSomething = &H02
then CommandDoSomething is &H02 ... unchangeable!
maybe you're thinking at something like this:
DIM GLOBAL_LOW_BATT_THRESH as BYte
Const Const_LOW_BATT_THRESH = &H02
Const Const_LOW_BATT_THRESH_DEFAULT = &H18
...
GLOBAL_LOW_BATT_THRESH = Const_LOW_BATT_THRESH_DEFAULT
do
...
loop end.
best, michael
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TSEYFARTH
Joined: 01 Jul 2006
Posts: 1054
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| Posted: Tue Jul 29, 2014 7:00 am Post subject: |
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Hi Six1,
Thank you for your response!
I agree:
| Quote: | it's not realy clear to me...
A Constant is a non editable constant value. You will define it in Sourcecode and this is, what it is... uneditable.
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That, in and of itself is the question. This is an effort to port C to BASCOM.... So before going through a lot of work to create a seemingly obvious solution, I wanted to ask others. There is a lot in BASCOM that I am not aware of, so it made sense to ask a really crazy question.
In C, they must have some kind of macro that does this:
| Quote: | Number Name Default Summary
0x0002 GLOBAL_LOW_BATT_THRESH 0x18 Low battery threshold
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Where '0x0002' is represented by the term "GLOBAL_LOW_BATT_THRESH" and the term has a default value - which in and of itself indicates that it is a variable. But again, wanted to ask the group since I am not aware of all the cool features of BASCOM.
Thanks again,
Tim |
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six1
Joined: 27 Feb 2009
Posts: 553
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| Posted: Tue Jul 29, 2014 7:21 am Post subject: |
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Hi Tim,
If you define a constant in your source, every location named with constant name is replaced by compiler with the constant value!
It's value is well known by the compiler!
A Variable is inside the variable memory (RAM)
It's value can't be known by compiler, because it can change during programm execution.
Theoreticaly you can change values inside ATmega programm memory by calling Bootloader Section... but this is a special case and not what you want to know 
If you define a variable, space will be reserved by compiler by the variable type (i.e. WORD will be reserve two Byte)
Every access to the variable during programm execturion will be linked to memory location of Variable.
Do you see the differences?
best, michael
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TSEYFARTH
Joined: 01 Jul 2006
Posts: 1054
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| Posted: Tue Jul 29, 2014 7:31 am Post subject: |
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Hi Six1.
I do understand. Bottom line, what they do in that C example is not possible in BASCOM.
So be it and confirmed. - again, just looking to be sure that there were no alternatives!
Thank you again!
Tim |
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albertsm
Joined: 09 Apr 2004
Posts: 5921
Location: Holland
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| Posted: Tue Jul 29, 2014 9:15 am Post subject: |
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you can not change the value of a constant in C either. why did they name it a constant otherwise?
a constant like PI has a fixed value that does not change.
i also do not see a CONST in your code. it appears you have a property. this is just a variable which can have a default value and which you can alter.
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Mark |
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six1
Joined: 27 Feb 2009
Posts: 553
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| Posted: Tue Jul 29, 2014 10:05 am Post subject: |
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Hi Tim,
maybe your copied code was only part...
if there is a "#define" before this:
0x0002 GLOBAL_LOW_BATT_THRESH 0x18 Low battery threshold
then the variable "GLOBAL_LOW_BATT_THRESH " will be later in sourcecode defined!
i.e.: Byte GLOBAL_LOW_BATT_THRESH = 0xd4
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MWS
Joined: 22 Aug 2009
Posts: 2262
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| Posted: Tue Jul 29, 2014 1:45 pm Post subject: |
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| six1 wrote: | maybe your copied code was only part...
if there is a "#define" before this: |
This is no copied code, it is the description of the API interface for Silabs Si446x series, which is to reveal by a google for some of the keywords.
http://nicerf.com/manage/upfile/indexbanner/635231050196868750.pdf
Why do I just think, it would have been the duty of the TO to show this, and not let people run around in riddles?
To interface with the API, or maybe rebuild parts of it in Bascom would look like that:
| Code: | Const GLOBAL_LOW_BATT_THRESH = 0x0002 |
A separate table needs to be set up for the defaults, where they can be looked up based on the given constant.
Edit:
Another, more memory saving way would be:
| Code: | Const GLOBAL_LOW_BATT_THRESH = 0x0002
Const GLOBAL_LOW_BATT_THRESH_default = 0x18 |
It's more writing work, but this way the compiler is able to use/resolve only the constants required by code and doesn't has to keep all the defaults in flash.
No other way, as far I can see, as a Bascom constant can use only one argument. |
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TSEYFARTH
Joined: 01 Jul 2006
Posts: 1054
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| Posted: Tue Jul 29, 2014 8:43 pm Post subject: |
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Hello all and thank you for your responses!
Please understand that I am absolutely struggling with this C stuff! Always have but hope one day not to - although I run away from it like the plague 
1. I know a Constant is just that, a constant value that cannot change - hence the word.
2. As MWS pointed out, I was not copying code, but the data sheet; but was trying to find a way to set the wording as a Const for the Property in a readable manner with an English Word, and THEN give it a starting value.
| Quote: |
To interface with the API, or maybe rebuild parts of it in Bascom would look like that:
Code:
Const GLOBAL_LOW_BATT_THRESH = 0x0002
A separate table needs to be set up for the defaults, where they can be looked up based on the given constant.
Edit:
Another, more memory saving way would be:
Code:
Const GLOBAL_LOW_BATT_THRESH = 0x0002
Const GLOBAL_LOW_BATT_THRESH_default = 0x18
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MWS, your suggestion may work, it would require sending the GLOBAL_LOW_BATT_THRESH and GLOBAL_LOW_BATT_THRESH_default - so the command is sent along with the value - {this may not be the actual format to send BTW, just for discussion sake herein}.
In terms of sample code (that supposedly works) , what I have is a list of defines (not really related to above or the question).
| Code: |
#define RADIO_CONFIGURATION_DATA_ARRAY { \
0x07, RF_POWER_UP, \
0x07, RF_GPIO_PIN_CFG, \
0x05, RF_GLOBAL_XO_TUNE_1, \
0x05, RF_GLOBAL_CONFIG_1, \
0x06, RF_INT_CTL_ENABLE_2, \
0x08, RF_FRR_CTL_A_MODE_4, \
0x0D, RF_PREAMBLE_TX_LENGTH_9, \
0x09, RF_SYNC_CONFIG_5, \
0x05, RF_PKT_CRC_CONFIG_1, \
0x05, RF_PKT_CONFIG1_1, \
0x07, RF_PKT_LEN_3, \
0x10, RF_PKT_FIELD_1_LENGTH_12_8_12, \
0x0C, RF_PKT_FIELD_4_LENGTH_12_8_8, \
0x10, RF_MODEM_MOD_TYPE_12, \
0x05, RF_MODEM_FREQ_DEV_0_1, \
0x0C, RF_MODEM_TX_RAMP_DELAY_8, \
0x0D, RF_MODEM_BCR_OSR_1_9, \
0x0B, RF_MODEM_AFC_GEAR_7, \
0x05, RF_MODEM_AGC_CONTROL_1, \
0x0D, RF_MODEM_AGC_WINDOW_SIZE_9, \
0x0F, RF_MODEM_OOK_CNT1_11, \
0x05, RF_MODEM_RSSI_COMP_1, \
0x05, RF_MODEM_CLKGEN_BAND_1, \
0x10, RF_MODEM_CHFLT_RX1_CHFLT_COE13_7_0_12, \
0x10, RF_MODEM_CHFLT_RX1_CHFLT_COE1_7_0_12, \
0x10, RF_MODEM_CHFLT_RX2_CHFLT_COE7_7_0_12, \
0x08, RF_PA_MODE_4, \
0x0B, RF_SYNTH_PFDCP_CPFF_7, \
0x10, RF_MATCH_VALUE_1_12, \
0x0C, RF_FREQ_CONTROL_INTE_8, \
0x00 \
}
const u8 RFM24_CONFIGURATION_DATA[]=RADIO_CONFIGURATION_DATA_ARRAY;
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WHAT I am looking for in BASCOM, is a way to set up the Property List, in human readable form, that has a default value that can also be changed. So yes, a combination of a Const (for the humand readable name) and then a Variable. This is one reason why I thought of an Alias - but do not think an Alias can really be used that way.
Something perhaps silly like:
GLOBAL_LOW_BATT_THRESH Alias 0x0002
GLOBAL_LOW_BATT_THRESH = 0x18 'Low battery threshold0x18 'Low battery threshold
I realize I am not explaining this all that well, but that is due to the fact that I do not know what I am doing with this! And not ashamed to admit it!
The whole reason behind doing this, is to make it easy to read and understand. A simple Data command could be used, but that is harder to read and understand down the road when one does not remember what &H02 property is... Oh yea, it was the GLOBAL_LOW_BATT_THRESH property!
See what I mean everyone?
Again, thank you for your responses! Much much appreciated!
Tim |
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MWS
Joined: 22 Aug 2009
Posts: 2262
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| Posted: Wed Jul 30, 2014 3:26 am Post subject: |
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You might want to work your way through this:
http://community.silabs.com/mgrfq63796/attachments/mgrfq63796/4/894/1/Radio_Header_Migration.pdf
A #define in C does simply text replacement, in this case it connects human readable identifiers with the corresponding value. So far it equals to a Bascom constant, where at compile-time each occurrence of the constant is replaced with its value.
What's different here is, that the const u8 RFM... will put the defined values into flash, which equals Bascom's Data statements. From there it can processed in order for init and other purposes.
An equivalent would be:
| Code: | Const myconst1 = 14
Const myconst2 = 33
Const myconst3 = 69
...
const_data:
Data myconst1, myconst2, myconst3 |
Your const/alias stuff won't work, but guess you found that out already.
That still does not solve the problem with the default values, you can store them in a separate Data statements. Beside sequential processing them in order with the order of constants, the problem is to connect the defaults directly to the constants, means you can't tell a default by the name of the constant.
So another approach would be to use the constants as index value and retrieve corresponding values from Data statements via lookup. The disadvantage is, it blows up the code and the constants can't be directly used, instead in every case the call of a function is neccessary, which retrieves the value(s) from its keys.
| Code: | Const myconst1 = 0
Const myconst2 = 1
Const myconst3 = 2
...
const_data:
Data 14, 33, 69
const_data_defaults:
Data 65, 11, 87 |
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TSEYFARTH
Joined: 01 Jul 2006
Posts: 1054
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| Posted: Wed Jul 30, 2014 5:58 am Post subject: |
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Thank you MWS.
I appreciate your time and the detailed descriptions.
I actually did not try the Alias since they are normally used to create an alias to a specific port, not a variable etc.
Again, thank you. The descriptive BASCOM equivalents are what I was after and now, having a surface understanding of these, will help tremendously.
BTW, the whole goal was to create code that could be shared, and easily understood quickly without having detailed knowledge of the data sheet(s) or devices. Just plain easy reading.
Thanks again to your and all!
Tim |
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EDC
Joined: 26 Mar 2014
Posts: 971
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| Posted: Wed Jul 30, 2014 8:13 am Post subject: |
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| Quote: | | really crazy question |
What think about Macro? Macro You can create and name, then use in code. Macro is small but/and don`t have Return |
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six1
Joined: 27 Feb 2009
Posts: 553
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| Posted: Wed Jul 30, 2014 8:16 am Post subject: |
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Hi Tim,
after reading the AN625 documentation, it is clear to me.
| Code: |
Number Name Default Summary
0x0002 GLOBAL_LOW_BATT_THRESH 0x18 Low battery threshold
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NUMBER seams to be a register inside the Chip,
DEFAULT is the default value before any changes done to the chip.
NAME is the human readable name of this register.
so a NAME has two informations: the register address and the register value.
a way could be:
| Code: |
'define Registers
Const REG_GLOBAL_LOW_BATT_THRESH = &H0002
...
'define variables
DIM GLOBAL_LOW_BATT_THRESH as Byte
....
GLOBAL_LOW_BATT_THRESH = reader_function( REG_GLOBAL_LOW_BATT_THRESH )
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best, michael
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MWS
Joined: 22 Aug 2009
Posts: 2262
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| Posted: Wed Jul 30, 2014 8:26 am Post subject: |
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| TSEYFARTH wrote: | | I actually did not try the Alias since they are normally used to create an alias to a specific port, not a variable etc. |
The problem with Alias is, that you would get another name for a constant, but what you need here is another value for the same constant.
Maybe, depending on request, this could be something to implement into the compiler. My guess is, that it would take not too many efforts.
An array of constants:
| Code: | 'classic use:
Const myconst = 123
'advanced use:
Const myconstarr(3) = 15, 57, 32
Const myinit = 1
Const myref = 2
Const myinfo = 3
'...
Dim B As Byte
B = myconstarr(myref) ' B = 57 |
But it's only an idea. The benefit is, if something is to resolve in compile time, it won't use up flash. So, if for example 100 constants are defined, but the code uses only one, the compiler will only have to keep this one in flash. If similar is done using Data, a library has to contain all values, which are consequently written into flash, and the right one is selected at run time.
Whether this may help you in your project, I'm not so sure, as a short look told me that the circuit needs some init sequence, which is pushed via SPI into the circuit. For this purpose you need all these values in flash and such an array of constants maybe only makes the code structure more clear, but won't save any bytes.
| Quote: | | BTW, the whole goal was to create code that could be shared, and easily understood quickly without having detailed knowledge of the data sheet(s) or devices. Just plain easy reading. |
That's always the idea behind an interface to a library, as it makes no sense, if the user has to find out what &h03 means. |
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mariofer
Joined: 07 Aug 2006
Posts: 23
Location: center italy
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| Posted: Wed Sep 16, 2015 12:13 am Post subject: |
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....
Maybe, depending on request, this could be something to implement into the compiler. My guess is, that it would take not too many efforts.
An array of constants:
| Code: | 'classic use:
Const myconst = 123
'advanced use:
Const myconstarr(3) = 15, 57, 32
Const myinit = 1
Const myref = 2
Const myinfo = 3
'...
Dim B As Byte
B = myconstarr(myref) ' B = 57 |
Hello
i try to compile this code , because i need to use an array of constant , but don't work .. the compiler get ..() not be used for constant
how can I create an array of byte (mono dim if to easy) of constant like for use same function for passing data array or var in ram/rom (like C) ?
const unsigned char pippo[]={1,2,3,4,5,6,7,8...}
dim pluto(xx) as byte
dim pos as byte
dim val as byte
pluto(1)=1
pluto(2)=2
..
pos=1
val=pippo(pos) it's possible ?
....
sub foo_ram_rom( pluto(),pos ) 'use ram array OK
sub foo_ram_rom(pippo(),pos ) 'use rom array ??
..
it's possible to use this single function for all type ?
b.r.
Mario |
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