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long bit fields

I am using the SPI to access a couple of 20 & 24 bit A/D converters which have some digital status bits preceding the reading. I already have some C code written (for another CPU) that defines the incoming data structure as a unsigned long. The Keil compiler, however, says I must use char or integer size bit fields. Is there an easy way around this without having to hand code the byte manipulation code manually?

Parents

0 mike simmons over 24 years ago in reply to Gary Culp

Here is a simplified example.

typedef struct {
 unsigned long det_in     :4,   /*compliance & short detection bits */
               Brd_rev    :4,   /* board / pal revision  */
               nu        :4,    /* not used as of 8/2000 */
               AD_data    :20;  /* 0=-max, 0x80000=0v, fffff=+max */
              } Bridge_brd_Rx_Type;  /* for each bridge card */

I do use this variable type in a union of however many longs it takes.My end goal is to point a PEC register at this structure, let the SPI run, and then access the different bit fields as

 { long reading; char revision;
reading = Brdg1.AD_data;
revision = Brdg1.Brd_rev;
...
 }

Reply

0 mike simmons over 24 years ago in reply to Gary Culp

Here is a simplified example.

typedef struct {
 unsigned long det_in     :4,   /*compliance & short detection bits */
               Brd_rev    :4,   /* board / pal revision  */
               nu        :4,    /* not used as of 8/2000 */
               AD_data    :20;  /* 0=-max, 0x80000=0v, fffff=+max */
              } Bridge_brd_Rx_Type;  /* for each bridge card */

I do use this variable type in a union of however many longs it takes.My end goal is to point a PEC register at this structure, let the SPI run, and then access the different bit fields as

 { long reading; char revision;
reading = Brdg1.AD_data;
revision = Brdg1.Brd_rev;
...
 }

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