uart waveform

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pcls1026
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uart waveform

Postby pcls1026 » Thu Oct 31, 2019 1:34 pm

I have a simple script to run UART 3 on my OpenMV Cam M7. I have attached it.

The UART voltage waveform does not seem to be correct.
I have the scope probe attached to pin 4 of the Cam M7.
I have the probe ground attached to the GND pin of the Cam M7.
The script sends chr(24), binary '00011000' from the UART3.
The waveform voltage output is ---- 3.26 Volts for 418 us----2.95 Volts for 208 us----3.26 Volts for 312us.

The bit pattern timing is correct, however THE VOLTAGES ARE WRONG.

Jim
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uartsimple_1.py
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kwagyeman
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Re: uart waveform

Postby kwagyeman » Thu Oct 31, 2019 1:56 pm

Does the UART not work when attached to a receiving device? We don't have analog control of the I/O. In uart mode its digital via the I/O pins. They just go between hi and lo.
Nyamekye,
pcls1026
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Re: uart waveform

Postby pcls1026 » Thu Oct 31, 2019 5:40 pm

I will try it hooked up to a microchip dsp33ep256mp on board uart and see if sends the correct wave form.
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iabdalkader
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Re: uart waveform

Postby iabdalkader » Fri Nov 01, 2019 3:07 pm

I just tested this and the voltage levels seem fine. Note I'm sending chr(20) (or 00010100)
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pcls1026
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Re: uart waveform

Postby pcls1026 » Sat Nov 02, 2019 6:30 pm

Hi,
That is exactly what I would expect to see.
My cam7 pin 4 is high before I start my script (attached) and remains high during the uart.write command.
I fear my cam7 microprocessor uart 3 transmitter has failed. The uart 3 WILL receive a write from my DSP with no problem.

Also, The PC cannot find the cam7 SD card.

Can I mail you my cam7 so you can see if the thing is working correctly. If it is not, I will buy a new one.
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kwagyeman
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Re: uart waveform

Postby kwagyeman » Sat Nov 02, 2019 6:37 pm

It could be broken. It's not impossible to damage the chip. We don't have a return department and can't diagnose problems. So, you may need to buy a new unit.

I'll look at your script when I get home.
Nyamekye,
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iabdalkader
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Re: uart waveform

Postby iabdalkader » Sat Nov 02, 2019 6:42 pm

There's nothing wrong with your scripts (at least not the first one which I tested)..I can only guess from here, but maybe that pin is shorting with the pin next to it. I'd check the solder on the pin header, sometimes it shorts if excessive solder was used.
pcls1026
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Re: uart waveform

Postby pcls1026 » Sat Nov 02, 2019 8:38 pm

I checked the soldering and re-soldered the pin. Nothing changed.

How about finding the SD card?

Jim
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kwagyeman
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Re: uart waveform

Postby kwagyeman » Sat Nov 02, 2019 9:16 pm

That would just be related to how your SD card is formatted. We support FAT16/32 or exFAT.
Nyamekye,
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iabdalkader
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Re: uart waveform

Postby iabdalkader » Sat Nov 02, 2019 9:28 pm

pcls1026 wrote:
Sat Nov 02, 2019 8:38 pm
I checked the soldering and re-soldered the pin. Nothing changed.

How about finding the SD card?

Jim
That won't help much, if you're determined to find the cause you should do a continuity test with a multimeter (test the pin with every other pin). The card should be detected if it's formatted to fat or exfat, note the direction of the pins when inserting the card. There might be dust in the uSD connector... If all fails, maybe the camera was damaged somehow.

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