How do I change data type float to hex?

RE: How do I change data type float to hex?

ovrebekk — Tue, 30 Aug 2022 17:34:03 GMT

Hi William

Good to hear you found a way to do it 🙂

Best regards
Torbjørn

RE: How do I change data type float to hex?

William_dev — Tue, 30 Aug 2022 08:30:25 GMT

Hi,

I Use Segger Embedded studio IDE.

I have done and solve the problem.

float value = 0.3f;

volatile uint16_t mtr[2] = {0, };

int main()
{
    *(float*)mtr = value;
    //mtr[1] = 0x3E99, mtr[0] = 0x999A
}

Best regards,

William

RE: How do I change data type float to hex?

ovrebekk — Tue, 30 Aug 2022 08:22:03 GMT

Which IDE/compiler are you using?

I modified one of the standard SDK examples to run the code I shared, and it build without problems:
devzone.nordicsemi.com/.../294158_5F00_float_5F00_test.zip

I tested it with 0.3 assigned to the float, and got the following log output:

<info> app: Float conversion test
<info> app: 999A - 3E99

I am using Segger Embedded Studio, and SDK v17.1.0 for this test, but I would expect the code to run fine in other compilers also.

Best regards
Torbjørn

RE: How do I change data type float to hex?

William_dev — Mon, 29 Aug 2022 09:06:12 GMT

Let me show you the neighboring example below.

float value = 0.3; // 0x3e99999a

volatile uint16_t mtr[2] = {0, };

/* Value should be change to mtr[1], mtr[0]  */
mtr[1] = 0x3e99;
mtr[0] = 0x999a;

How can I make float value to 16 bit hex value?

RE: How do I change data type float to hex?

William_dev — Mon, 29 Aug 2022 07:11:39 GMT

Hi Torbjørn,

I did your recommend code, but it work some errors.

1. cannot convert to a pointer type

2. invalid initializer

3. data definition has no type or storage class [-Werror]

4. cannot convert to a pointer type

RE: How do I change data type float to hex?

ovrebekk — Wed, 24 Aug 2022 13:31:23 GMT

Hi William

In that case you should be able to copy the raw value of the upper and lower bytes of your float directly into your two uint16 variables.

A trick to do this is to get a pointer to your float, cast it to a uint16 pointer, and then dereference the pointer again to only access the lower and upper 16 bits.

Please try the following code:

float measure_value;
uint16_t buffer[2];
buffer[0] = ((uint16_t*)&measure_value)[0];
buffer[1] = ((uint16_t*)&measure_value)[1];

Best regards
Torbjørn

RE: How do I change data type float to hex?

William_dev — Wed, 24 Aug 2022 08:11:25 GMT

Thank you for your quick reply.

I'd like to store value 0.0~12.7 convert to unsigned integer 16-bit, and the value will be express to two size of uint16_t array.

ex) uint16_t buffer[2] = {0x0000, 0x0000};

buffer[0] = measure_value(converted to hex);

buffer[1] = measure_value(converted to hex)<<16;

Best regards

William

RE: How do I change data type float to hex?

ovrebekk — Tue, 23 Aug 2022 10:40:55 GMT

As you probably know a float data type in C is stored in 32 bits, so if you want to convert a float value to 16 bits you will need to accept some loss of precision.

What kind of numbers do you need to store? Will they not contain a fractional part, only integer values below 2^16 (to fit in a unsigned 16 bit integer) ?

Best regards
Torbjørn