TMDSCNCD28379D: Using Printf with float numbers

Ehsan Qiyassi

Part Number: TMDSCNCD28379D
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi,

I'm trying to send an ADC reading to UART terminal. Sending the value as integer (register value) works fine but when I try to send the converted value, which is float, I run into an exception:

Working:

sprintf(msg, "\r\n%s = %d [V]" , "Voltage = ", ADC_readResult(Vbat_BASE, ADC_SOC_NUMBER0)) ;

Not working:

float vBat ;

vBat = ( ADC_readResult(Vbat_BASE, ADC_SOC_NUMBER0) )*( 0.1871F ) ;

sprintf(msg, "\r\n%s = %g [V]" , "Voltage = ", vBat) ;

Here's the screen shot of where the exception happens:

which shows this is the step where vBat is converted to string using %g

Here's a screen shot of the exception which I don't understand:

Any help is much appreciated.

6 months ago

0 Ehsan Qiyassi 6 months ago

Prodigy 80 points

Any thoughts? Anyone?

0 Masoud Farhadi 5 months ago in reply to Ehsan Qiyassi

TI__Expert 6030 points

Hi Ehsan,

This is due to insufficient stack or heap memory. You can re-run the same sprintf call with %g or %f with adequate stack assigned to the correct memory region. After increasing stack size, update the linker command file to allocate enough memory.

Please refer to these threads for more information:

(+) TMS320F28379D: Error #1558-D 64 bit floating point not allowed for sprintf - C2000 microcontrollers forum - C2000Tm︎ microcontrollers - TI E2E support forums

(+) TMS320F280025C: Can't use sprintf for the error '64bit floating point operations are not allowed' - C2000 microcontrollers forum - C2000Tm︎ microcontrollers - TI E2E support forums

Best Regards,

Masoud

0 Ehsan Qiyassi 5 months ago in reply to Masoud Farhadi

Prodigy 80 points

Hi Masoud,

Thanks for the suggestion. The two thread you've linked deal with compiler errors. I'm dealing with runtime error/crash.

I had to write my own float to string conversion function which for the time being doesn't seem to cause a crash.

I'm suspecting that the %g and %f formatting in the snprintf library cannot be interrupted safely. Because I've noticed that during the conversion (servicing the interrupt) I get another interrupt.

This issue is certainly worth looking into by your team, since writing this basic functionality, even with limited features and not testing all the edge cases, is very time-consuming for users like me.

0 Masoud Farhadi 5 months ago in reply to Ehsan Qiyassi

TI__Expert 6030 points

Hello,

TI’s C/C++ compiler offers a --printf_support flag that controls whether floating point formatting is enabled in printf/sprintf:

- full – Supports all format specifiers (includes floats) — this is the default behavior.

- nofloat – Excludes support for %f, %g, %e, and their uppercase versions.

- minimal – Supports only %d, %s, %c, %x, %%—no floats or precision flags.

If your project is built with nofloat or minimal, using %g or similar specifiers leads to undefined behavior, often resulting in crashes or exceptions.

You should check --printf_support in CCS and ensure it’s set to full and ensure the availability of --float_support=fpu32 and the corresponding runtime library (e.g., rts2800_fpu32.lib). Also, since floating point printf consumes significantly more stack and heap, you’ll have to allocate enough memory to avoid crashes. The crash should no longer occur if the build is correctly configured.

Best Regards,

Masoud

0 Ehsan Qiyassi 5 months ago in reply to Masoud Farhadi

Prodigy 80 points

Hi,

The printf support is set to full. rts2800_fpu32.lib is also available and used in the build. I'll increase the stack size to see if it helps. How can I change the size of the heap?

0 Masoud Farhadi 5 months ago in reply to Ehsan Qiyassi

TI__Expert 6030 points

The heap is just a linker-allocated block of RAM. You can change it in here:

Right-click your project >> Select "Properties" >> Go to Build >> C2000 Linker >> Basic Options

On the right, you find heap size (–heap_size) and stack size (–stack_size).

Sometimes projects override heap/stack in their linker file (.cmd file), something like: --stack_size=0x200, where you can manually bump them up.

Also, it's good to monitor CCS Memory Allocation view to ensure you’re not overrunning available RAM.

Best Regards,

Masoud

0 Ehsan Qiyassi 5 months ago in reply to Masoud Farhadi

Prodigy 80 points

Thanks Masoud. I missed the heap size allocation since it was left blank. I have combined two RAM blocks together, through sysConfig, for the total length of 0x6d5 (according to the generated .map file), out of which 0x200 is assigned to Stack. Does this mean I could assign the unused part (0x2d5) to the Heap memory? I don't see heap location specified anywhere in the .map or .cmnd file

0 Ehsan Qiyassi 5 months ago in reply to Ehsan Qiyassi

Prodigy 80 points

btw, do you know if printf library uses dynamic memory allocation?

0 Masoud Farhadi 5 months ago in reply to Ehsan Qiyassi

TI__Expert 6030 points

The C runtime heap lives in the .esysmem section. Its size is controlled by the linker option --heap_size. You can set it in CCS:

Right-click your project >> Select "Properties" >> Go to Build >> C2000 Linker >> Basic Options

If your project generates a linker command file, make sure .esysmem is actually placed into a RAM region that has enough free space. A snippet looks like:

SECTIONS

{

   .stack   : > RAMLS5

   .esysmem : > RAMLS5   /* heap */

}

Best regards,

Masoud

0 Masoud Farhadi 5 months ago in reply to Ehsan Qiyassi

TI__Expert 6030 points

The printf family typically does not allocate dynamic memory for sprintf/snprintf. They write into the buffer you supply. Heap is mainly for APIs like malloc/new.

Best regards,

Masoud

0 Ehsan Qiyassi 5 months ago in reply to Masoud Farhadi

Prodigy 80 points

Just an update. Increasing the Stack and Heap size didn't resolve the issue. Memory allocation window also shows sufficient memory assigned for them. I'm using %g on CPU2 successfully which rules out any build issues, imo. It just seems that printf is not thread-safe,as the only difference between CPU1 and CPU2 is that CPU1 is handling the pwm generated interrupts.

0 Masoud Farhadi 5 months ago in reply to Ehsan Qiyassi

TI__Expert 6030 points

Glad to here that issue resolved! I marked the comment as resolved for future reference.

Best Regards,

Masoud

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TMDSCNCD28379D: Using Printf with float numbers