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xtremeroboz
Joined: 15 Mar 2019
Posts: 2
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| Function with xfer name of Stream |
 Posted: Fri Mar 15, 2019 1:49 am |
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Hi Everyone
I try to create a function with xfer, this is part of my code:
| Code: |
#use spi (MASTER, CLK=SPI_CLOCK, DI=SPI_DATA, LOAD=SPI_LOAD, LOAD_ACTIVE=1, MODE=2, BITS=8, STREAM=SHIFT_REG_A, MSB_FIRST)
#use spi (MASTER, CLK=SPI_CLOCK, DI=SPI_DATA, LOAD=SPI_LOAD, LOAD_ACTIVE=1, MODE=1, BITS=8, STREAM=SHIFT_REG_B, MSB_FIRST)
#use spi (MASTER, CLK=SPI_CLOCK, DI=SPI_DATA, LOAD=SPI_LOAD, LOAD_ACTIVE=1, MODE=0, BITS=8, STREAM=SHIFT_REG_C, MSB_FIRST)
//This is My Function
unsigned int ReadShiftRegister(char NUM_SHIFT_REGISTER)
{
unsigned int VAL_SHIFT_REGISTER;
VAL_SHIFT_REGISTER = spi_xfer(NUM_SHIFT_REGISTER, 0x00);
return VAL_SHIFT_REGISTER;
}
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I have trouble with variable NUM_SHIFT_REGISTER
*** Error 130 "shifts.c" Line 315(51,55): Stream must be a constant in the valid range ::
Thanks for your help |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Fri Mar 15, 2019 3:20 am |
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The point is that stream names _have to be constants_.
If you want to use a variable, you have to code this yourself.
Understand that when a stream name is used for a function like SPI_XFER,
the code to physically access the named stream is substituted.
So if you want to use a variable to access three different streams, you
would have to just use a variable, and a switch statement to call the
three different output routines. So:
| Code: |
//This is My Function
unsigned int ReadShiftRegister(char NUM_SHIFT_REGISTER)
{
unsigned int VAL_SHIFT_REGISTER;
switch (NUM_SHIFT_REGISTER) {
case 0:
VAL_SHIFT_REGISTER = spi_xfer(SHIFT_REG_A_REGISTER, 0x00);
break;
case 1:
VAL_SHIFT_REGISTER = spi_xfer(SHIFT_REG_B_REGISTER, 0x00);
break;
case 2:
VAL_SHIFT_REGISTER = spi_xfer(SHIFT_REG_B_REGISTER, 0x00);
break;
}
return VAL_SHIFT_REGISTER;
}
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As a general 'style comment', in C, it is standard to reserve 'ALL CAPITALS'
for things that are #defined, or otherwise fixed (so typedefs for example).
So better to call a variable that accesses a shift register number
'Val_Shift_Register'.
As a standard, it helps when debugging code, to quickly be able to
distinguish things that are variables from things that are not.
Just a useful 'tip' to help code legibility. |
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dluu13
Joined: 28 Sep 2018
Posts: 395
Location: Toronto, ON
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| Posted: Fri Mar 15, 2019 8:05 am |
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| Ttelmah wrote: | As a general 'style comment', in C, it is standard to reserve 'ALL CAPITALS'
for things that are #defined, or otherwise fixed (so typedefs for example).
|
This is important, especially when #case is used. I had a bunch of stream names stop working suddenly when I added #case. Apparently the compiler capitalized the stream names. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Fri Mar 15, 2019 8:53 am |
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Yes, the one for streams is very important. CCS defaults internally to
capitalising all stream names, and if you implement #case, and use a
stream name that is not capitalised, it won't work... |
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temtronic
Joined: 01 Jul 2010
Posts: 9098
Location: Greensville,Ontario
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| Posted: Fri Mar 15, 2019 1:12 pm |
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BTDT,, got stumped for quite awhile..... 
Jay |
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