Defining array of bytes for use to call later in C program

Question

Initializing a SI labs radio, the software develops a header file as well as a patch file. first part is, depending on the patch file it outputs different ways. here is a snippet of each patch:

Rev B patch:

#define SI446X_PATCH_CMDS                   \
{ 0x04,0x11,0xF7,0x76,0x00,0x00,0xA6,0x82 }, \
{ 0x05,0x61,0xE6,0x82,0x5E,0xB7,0xFB,0x93 }, \
{ 0x05,0x1E,0x12,0xBD,0x5A,0xC2,0x52,0x41 }, \
{ 0xE7,0xF4,0xDF,0x6A,0x24,0xD9,0xBA,0x31 }, \

OR

Rev C patch:

    #define SI446X_PATCH_CMDS                   \
0x08,0x04,0x21,0x71,0x4B,0x00,0x00,0xDC,0x95, \
0x08,0x05,0xA6,0x22,0x21,0xF0,0x41,0x5B,0x26, \
0x08,0xE2,0x2F,0x1C,0xBB,0x0A,0xA8,0x94,0x28, \
0x08,0x05,0x87,0x67,0xE2,0x58,0x1A,0x07,0x5B, \

Now this will be hardcoded into the software and either one commented out. but it must have been done this way for a reason and i dont understand it. for initial testing i placed each line of 8 bytes (as it needs to be pushed over SPI this way) into an array and then created a pointer to the array since the length isnt necessary as they are all 8 bytes like i said. iss there a more intelligent way i should cade this based on the way it is presented?

uint8_t array_1[8] = { 0x04, 0x11, 0xF7, 0x76, 0x00, 0x00, 0xA6, 0x82 };
uint8_t array_2[8] = { 0x05, 0x61, 0xE6, 0x82, 0x5E, 0xB7, 0xFB, 0x93 };

uint8_t *theArrays[] = { array_1, array_2, array_3, array_4, array_5, array_6,
        array_7, array_8, array_9, array_10, array_11, array_12, array_13,

I then program the SPI using this code and manually typed in the qty into a for loop as i cant get sizeof from the pointer array.

HAL_SPI_Transmit(&hspi1, theArrays[i], 8, 50);

Gerhardh · Accepted Answer · 2022-09-29 14:44:27Z

2

These macros just make things a bit easier. Assuming the number of (sub)arrays in both macros matches the number of arrays in your array of pointers, your code would look like this in full version:

uint8_t array_1[8] = { 0x04, 0x11, 0xF7, 0x76, 0x00, 0x00, 0xA6, 0x82 };
uint8_t array_2[8] = { 0x05, 0x61, 0xE6, 0x82, 0x5E, 0xB7, 0xFB, 0x93 };
uint8_t array_3[8] = ...
uint8_t array_4[8] = ...
uint8_t array_...
uint8_t array_12[8] = ...
uint8_t array_13[8] = ... 

uint8_t *theArrays[] = { array_1, array_2, array_3, array_4, array_5, array_6,
        array_7, array_8, array_9, array_10, array_11, array_12, array_13,

...
   HAL_SPI_Transmit(&hspi1, theArrays[i], 8, 50);

With these macros (stored in some nice header) you can just do this:

Revision B:

#define SPI_MESSAGE_SIZE 8
const uint8_t theArray[][SPI_MESSAGE_SIZE] = {SI446X_PATCH_CMDS};
_Static_assert(sizeof theArray/sizeof *theArray == SOME_EXPECTED_SIZE, "SI446X_PATCH_CMDS corrupt");
...
HAL_SPI_Transmit(&hspi1, theArrays[i], SPI_MESSAGE_SIZE, 50);

or in case of Revision C

#define SPI_MESSAGE_SIZE 8
const uint8_t theArray[] = {SI446X_PATCH_CMDS};
_Static_assert(sizeof theArray/sizeof *theArray == SOME_EXPECTED_SIZE, "SI446X_PATCH_CMDS corrupt");
...
// For Rev C, the array contains a <length> byte before the SPI data.
// Adjust addressing accordingly
uint8_t len = theArrays[i*(SPI_MESSAGE_SIZE+1)];
HAL_SPI_Transmit(&hspi1, &theArrays[i*(SPI_MESSAGE_SIZE+1)+1], len, 50);

The static assert was suggested by Lundin. I am not aware of the correct value to compare but there should be some useful define somewhere in Silabs Radio's headers.

edited Sep 29, 2022 at 14:44

answered Sep 29, 2022 at 13:54

Gerhardh

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10 Comments

Lundin Over a year ago

I use these Silabs radios too and this answer looks very similar to what I would have done as well. Optionally add _Static_assert(sizeof theArray/sizeof *theArray== SOME_EXPECTED_SIZE, "SI446X_PATCH_CMDS corrupt");

Ryan TC Over a year ago

I hand typed this out and am trying to avoid it if possible but in your example it seems this is still neccessary?

uint8_t array_1[8] = { 0x04, 0x11, 0xF7, 0x76, 0x00, 0x00, 0xA6, 0x82 }; uint8_t array_2[8] = { 0x05, 0x61, 0xE6, 0x82, 0x5E, 0xB7, 0xFB, 0x93 };

Lundin Over a year ago

@RyanTC Just use the const uint8_t theArray[][SPI_MESSAGE_SIZE] = {SI446X_PATCH_CMDS};. The hex blob should be in some header.

Gerhardh Over a year ago

@RyanTC No, all those arrays are replaced by a single one. That first code is the corresponding part to the snippets belos.

Lundin Over a year ago

@RyanTC Just keep that in mind when you send it over the SPI. Read the first byte, send the following "size read" number of bytes, repeat.

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