LAUNCHXL-F280039C: DSP execution speed

Haobo Zhang

Part Number: LAUNCHXL-F280039C
Other Parts Discussed in Thread: SYSCONFIG

Hi TI support team,

I discovered something I don't understand while working with the LAUNCHXL-F280039C eval board. The DSP is configured to run at 120 MHz as follows:

However, the DSP runs much more slowly than I expected. I imported a TI example, "led_ex1_blinky", and added a new GPIO output (IO.47) in SysConfig to measure the timing on the oscilloscope. I modified the sample program to toggle the pin before and after writing to the LED. The measured time (IO.47 from ON to OFF) is about 1.26us. Please see the code snippet below.

Is this slowness expected from this DSP (F280039C)? Or are there any settings or code I should check?

Thanks,

Haobo

7 days ago

0 Haobo Zhang 7 days ago

Prodigy 30 points

To clarify, the test program was running from RAM, not from Flash.

0 Haobo Zhang 5 days ago

Prodigy 30 points

Hi TI support team, would it be possible to provide any guidance on this issue?

Thanks,

Haobo

0 Stevan Duraskovic 5 days ago in reply to Haobo Zhang

TI__Expert 6740 points

Hello Haobo,

I will take a look and reply in timely manner.

0 Stevan Duraskovic 3 days ago in reply to Haobo Zhang

TI__Expert 6740 points

Hello Haobo,

Your measured timing is not a RAM performance problem — it's the overhead of the DriverLib GPIO_writePin() function. GPIO_writePin() abstracts hardware access for convenience, but at a significant performance cost by adding couple of lines.

To fix it replace your GPIO_writePin() calls with the HWREG macro or bit-field register access: (By stepping into the driverlib function you would see unnecessary lines that you can remove so you can keep just HWREG part).

// Set GPIO47 high (GPIO47 is in port B, bit 15)
HWREG(GPIODATA_BASE + GPIO_O_GPBSET) = (1UL << 15);

// Set GPIO47 low
HWREG(GPIODATA_BASE + GPIO_O_GPBCLEAR) = (1UL << 15);

0 Haobo Zhang 3 days ago in reply to Stevan Duraskovic

Prodigy 30 points

Thank you, Stevan. The suggested change restores the expected performance. After the following change, the measured time was reduced to 33ns.

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LAUNCHXL-F280039C: DSP execution speed