Hi Dialog,
I have designed a custom PCB based on DA14682 that includes some other devices like an SD Card and etc. When I configure one pin as an output and toggle that in high frequency (like SPI Clock or Timer output), the created signal overshoots and when this pin is SPI clock, SD Card doesn't work normally. Is there anyway to solve this problem?
- I have tested some other GPIOs for SPI clock and all of them have this problem.
- The SPI clock tested on 24, 12, 8, 6.85, 4, 2 and 1.14 MHz (both PLL96 and 16MHz Xtal).
- I have attached the wave signal output pictures.
Thank you in advance.
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Hi techteh,
I had a look at your attachments be aware that is a such a strange and unusual behavior. We have never seen this situation before. According to your screenshots, I saw that have 200mV per division which seems to not be correct. Is it 2Volt? If yes, the overshoot would be exceeding 5V. Is it possible to upload the schematics of your board? This would be very useful because it seems that is a hardware issue on your custom board. Also, can you please measure the output signal of a GPIO when nothing is connected to this pin and then let me know with the result?
Thanks, PM_Dialog
Hi,
Yes that is 2V per division.
I have attached the Schematics.
When I measure the output signal of a GPIO when nothing is connected to that, there is no differences.
Thanks.
Hi techteh,
谢谢你上传你的图表. According to the datasheet, you can only connect V33 or VDD1V8 and not the VUSB. If you have this voltage on the GPIOs, the limit voltage of the GPIO (3.45V in 3V3 mode) would be exceeded. Also, a possible reason why you get this kind of overshoot, is due to measurement problem, because the grounding of his oscilloscope is probably weak. Could you please let me know if you are measuring those waveforms when running on the battery or when USB is connected?
Thanks, PM_Dialog
Hi,
Thanks for your reply,
I've just checked what you said. In both situations of VBUS Connected or only BAT connected, I have that overshoot problem.
When I reduce frequency of the SPI clock, SD card works normally, so I think that this problem is because of this overshoot.
I have checked my micro program on "DA14681 Development Kit - Basic" and "DA14683 Development Kit USB" and there is no problem.
So I think this should be a hardware issue. Could you please check my schematics and say what would be the problem?
Thanks.
Hi techteh,
I have already checked your schematics and they seem to be correct. However I will double check them again. I suppose that would be a measurement issue due to the weak grounding of the oscilloscope.
Thanks, PM_Dialog