Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Gary, Refer to? The pa bias is derived from 12v tx line that is switched by a mosfet. It is not driven by gpio. The uln2003 have a very light loading and their input loading not worse than any other buffering gates. - f
If sBitx V1 schematic on github is correct,
Main board's C66 (0.1uF) is being driven directly by the pi.? Cap load without an added current limiting series resistor.
Surprised that so many TX controlled circuits on the sBitx main board are being driven directly by the pi, including setting bias of an amp.
I don't see the downside of having the TX node on the main board at 12V (with the appropriate required changes to adjust for the higher voltage).
There's already an inverting buffer on board. Use the 2 unused channels on the ULN2003A to take the 3.3V signal from the pi up to 12V with 500mA of drive.
Still wouldn't drive a cap directly.
Just my observation,
Gary
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
If sBitx V1 schematic on github is correct,
Main board's C66 (0.1uF) is being driven directly by the pi.? Cap load without an added current limiting series resistor.
Surprised that so many TX controlled circuits on the sBitx main board are being driven directly by the pi, including setting bias of an amp.
I don't see the downside of having the TX node on the main board at 12V (with the appropriate required changes to adjust for the higher voltage).
There's already an inverting buffer on board. Use the 2 unused channels on the ULN2003A to take the 3.3V signal from the pi up to 12V with 500mA of drive.
Still wouldn't drive a cap directly.
Just my observation,
Gary
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Paul The v2 does not use LM338, it uses a switching regulator. We also use a 7805 step down that feeds the 1117s. There are 3.3v zeners on all external facing gpio pins
- f
While I wait for my sbitx v2, I have noticed there are no 'backward facing' clamp diodes on the fixed regulators that prevent the regulated output voltage (VOUT) exceeding the input voltage (VIN) on power down conditions. I also think according to the data sheet LM338 a filter capacitor is required from the 'ADJ' pin to ground. The datasheets for both the LM338 and the AMS1117 recommend the? clamp diode and I think the AMS1117 is particularly sensitive in this respect. I remember many years ago my homebrew Z80 computer regularly blew the graphics eeprom until I did this.
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
While I wait for my sbitx v2, I have noticed there are no 'backward facing' clamp diodes on the fixed regulators that prevent the regulated output voltage (VOUT) exceeding the input voltage (VIN) on power down conditions. I also think according to the data sheet LM338 a filter capacitor is required from the 'ADJ' pin to ground. The datasheets for both the LM338 and the AMS1117 recommend the? clamp diode and I think the AMS1117 is particularly sensitive in this respect. I remember many years ago my homebrew Z80 computer regularly blew the graphics eeprom until I did this.
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Re: WSJT-x 2.6.1 and uBitx on Raspberry Pi
#ubitx
Thank you Ashhar.? If I understand what you are saying, with version 2.5.4 of WSJT-X it did not reset the USB port, but they changed something in the code for WSJT-X 2.6.1 so that it does reset the USB port?
-Dj
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
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On Tue, Apr 18, 2023 at 2:15?PM John Terrell, N6LN < N6LN@...> wrote: Lou, I remembered that post from Allison but I can¡¯t find it. What was the number of that post?
Jack?
N6LN
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Lou, I remembered that post from Allison but I can¡¯t find it. What was the number of that post?
Jack?
N6LN
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Alvin, that is fine, I¡¯m just would be really interested to know what I blew apart. That might help avoid a repeat!
Gordon
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On Apr 18, 2023, at 10:34, Evan Hand <elhandjr@...> wrote:
?Gordon,
I have the time and have done some forensics on other devices.? I am NOT a Raspberry Pi expert.? I DO have the SMD tools that I need.
With the above understanding, I would like to look into the cause of your RPi failure.? If there is someone who does have experience with RPi diagnostics, I would rather you send it to them.
Let's wait a few days to see if someone else approaches the challenge.? If not, then my QRZ email and address are good.
73
Evan
AC9TU
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Allison I found that post.? Do you have any drawings you can share? 73 Lou KI5FTY
On Tue, Apr 18, 2023 at 11:53?AM ajparent1/kb1gmx < kb1gmx@...> wrote: I found the Rpi output (and inputs) are fragile based on data sheets.
So one of the mods I made and wrote about maybe 5-6 months ago were to buffer all lines out
to the main board and and diodes and resistor to the inputs as well from the main board.
I've also done this with other Pi applications that do not use a direct plug in hat.
to date I've not fired a pi (or Arduino).
--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
I found the Rpi output (and inputs) are fragile based on data sheets.
So one of the mods I made and wrote about maybe 5-6 months ago were to buffer all lines out
to the main board and and diodes and resistor to the inputs as well from the main board.
I've also done this with other Pi applications that do not use a direct plug in hat.
to date I've not fired a pi (or Arduino).
--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Gordon,
I have the time and have done some forensics on other devices.? I am NOT a Raspberry Pi expert.? I DO have the SMD tools that I need.
With the above understanding, I would like to look into the cause of your RPi failure.? If there is someone who does have experience with RPi diagnostics, I would rather you send it to them.
Let's wait a few days to see if someone else approaches the challenge.? If not, then my QRZ email and address are good.
73
Evan
AC9TU
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Ashhar:
No worries my friend.? Glad you are doing some final checks on the software of the radios.? It gets here when it gets here.? Will have some time this summer to tinker with the software.? In the mean time, I just need to go and start digesting the software you have on the Github repository and other documentation you have prepared
73 de Darrell KT4WX
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
I don't have the time//ability to? "? It would be interesting to do the forensics on one of the dead RPis to see if that diode is shorted or open."
If someone is really an expert on failed rPi's and someway for me to ship them a DEAD RPi4 --- I'll be happy to ship them one so they can enlighten us all how I managed to destroy these!!!
Thanks, Gordon Kx4Z
On Tue, Apr 18, 2023 at 9:38?AM Evan Hand < elhandjr@...> wrote: John,
Trying the 3.3 volt (maybe 3.6 volt?)? with or without the resistor could not hurt.? The diode would add capacitance that might make the I2C decode an issue, so I would do the Zener first, then add the resistor.? Adding the 7805 regulators ahead of the LM1117 is a good idea.
Using diodes to drop the input voltage on QRP transceivers works well.? The current required by ORO transceivers, like the Sbitx, may make it a problem.? 10 amps with a .6 volt drop require 6 watts to be dissipated.? A buck or buck/boost converter might be better if the noise is not an issue.
I am waiting to buy a new oscilloscope with I2C decoding.? This may be a good project to test the capability.
We should also look at the long 5 volts run from the 5-volt buck converter to the RPi board.? We may need RF bypassing on it, moving the converter, or replacing the trace with a shielded wire that can handle the current.? I like Gordon's idea of modifying how the RPi gets its power.? There are protections on the USB-C connector that are not on the GPIO connector.? The RPi schematic has a 5-volt Zener on the input from the USB-C connector.? That would be connected to the 5-volt line on the GPIO.? I would think it would keep the voltage at 5 volts regardless of the supply.? It would be interesting to do the forensics on one of the dead RPis to see if that diode is shorted or open.
I also do not like that the power warning had to be turned off when powering from the GPIO connector.? Low voltage may be the issue, with the pulses indicated by the audio when WiFi is turned on.? We are back to Gordon's suggestion to power through the USB-C connector with the voltage warnings on to see if there is an issue.
The above are questions, not suggestions.
73
Evan
AC9TU
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
John,
Trying the 3.3 volt (maybe 3.6 volt?)? with or without the resistor could not hurt.? The diode would add capacitance that might make the I2C decode an issue, so I would do the Zener first, then add the resistor.? Adding the 7805 regulators ahead of the LM1117 is a good idea.
Using diodes to drop the input voltage on QRP transceivers works well.? The current required by ORO transceivers, like the Sbitx, may make it a problem.? 10 amps with a .6 volt drop require 6 watts to be dissipated.? A buck or buck/boost converter might be better if the noise is not an issue.
I am waiting to buy a new oscilloscope with I2C decoding.? This may be a good project to test the capability.
We should also look at the long 5 volts run from the 5-volt buck converter to the RPi board.? We may need RF bypassing on it, moving the converter, or replacing the trace with a shielded wire that can handle the current.? I like Gordon's idea of modifying how the RPi gets its power.? There are protections on the USB-C connector that are not on the GPIO connector.? The RPi schematic has a 5-volt Zener on the input from the USB-C connector.? That would be connected to the 5-volt line on the GPIO.? I would think it would keep the voltage at 5 volts regardless of the supply.? It would be interesting to do the forensics on one of the dead RPis to see if that diode is shorted or open.
I also do not like that the power warning had to be turned off when powering from the GPIO connector.? Low voltage may be the issue, with the pulses indicated by the audio when WiFi is turned on.? We are back to Gordon's suggestion to power through the USB-C connector with the voltage warnings on to see if there is an issue.
The above are questions, not suggestions.
73
Evan
AC9TU
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Mark, If you monitor the current draw of sbitx, it is well under 1A on receive. There is no way the rpi can draw more. There is some other reason, not low voltage. The low voltage warning happens anyway when you power it from the gpio pins instead of the usb port. - f
Could any of these failures be caused by low current supplied to the RPi by the radio? I have noticed that it I try to connect an NvME SSD drive to the USB port, it¡¯s operation is erratic. I have no problems with the same drive connected to a RPi 400 powered by a 3.5A wall wart supply. I believe the sBitx only supplies 2A.
Also, the instructions in install.txt say to disable the low voltage warning, which does display if not disabled. Does disabling the warning also disable any low voltage protection?
Lastly, can I power the RPi by its USB C port while it is in the sBitx or do I need to do something to disable the power coming from the radio?
--
73,
Mark, N8ME
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
Could any of these failures be caused by low current supplied to the RPi by the radio? I have noticed that it I try to connect an NvME SSD drive to the USB port, it¡¯s operation is erratic. I have no problems with the same drive connected to a RPi 400 powered by a 3.5A wall wart supply. I believe the sBitx only supplies 2A.
Also, the instructions in install.txt say to disable the low voltage warning, which does display if not disabled. Does disabling the warning also disable any low voltage protection?
Lastly, can I power the RPi by its USB C port while it is in the sBitx or do I need to do something to disable the power coming from the radio?
--
73,
Mark, N8ME
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Re: WSJT-x 2.6.1 and uBitx on Raspberry Pi
#ubitx
It has to do wit this: The usb port resets when reopened by wsjtx, on arduino this resets the arduino and the ubitx loses track of what was going on.
I had mentioned this to the wsjtx guys but they didn't seem interested in fixing it. - f
Hi Dj,
I don¡¯t remember the exact issues I had when trying to upgrade but I ended up doing the same thing: reverted back to 2.5.4. ?
Cheers, Scott
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Re: WSJT-x 2.6.1 and uBitx on Raspberry Pi
#ubitx
Hi Dj,
I don¡¯t remember the exact issues I had when trying to upgrade but I ended up doing the same thing: reverted back to 2.5.4. ?
Cheers, Scott
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Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
A 12V Zener might be well advised on the power line, and I bought a bunch anyway for the gates of the finals, but since my supply puts out 13.7V I wonder whether I should also put two or three regular diodes in series with it. I have seen the 5351¡¯s lm1117s fail twice, once simply shorting with smoke and simply dropping all power output to the 5351 and another time failing and sending 13.7v straight through to the 5351 which glowed orange in the chip¡¯s center before melting two pads, the latter which was fixed by removing and replacing it and the crystal oscillator with a 5351 breakout board. It¡¯s not as stable frequency wise but it¡¯ll do for now. I now protect the new lm1117 by putting a small 5V LDO 78L05 between the 13.7V rail and the new lm1117 which in turn provides the breakout board with 3.3V. The 5V supply to the 1117 also has a 47 uF electrolytic on its input. So far it works.
On the other hand the most recent failure did not involve the bitbanged I2C lines. Instead it involved the TX line output (GPIO4) failing to send a TX signal on PTT. Since this does not directly involve an lm1127 I have to assume that it failed because of a power surge from elsewhere, either a transient from the main power supply (in which case a 12 or 14V Zener on the main supply would be helpful) or else a higher voltage coming from rf somewhere. Either way if it¡¯s transient I doubt I¡¯ll be able to measure it when it happens. If there¡¯s no downside on putting 3.3V Zeners, with or without series resistors, on those three RPi lines, maybe it would help to do so. The right angle connector on the digital board has good exposure for adding small Zeners, and can easily be snapped open to insert a series 330 ohm resistor, and repaired if that interferes with the timing. Couldn¡¯t hurt to try, could it?
Jack
N6LN
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Ahh, ok.
I did not find the ver. of the first manual (I like the "hellov2 name, hi) so I asked.
Versioning of the .iso image is a must of course. Thanks for info and your help.
- P
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Dj Merrill
John Terrell, N6LN
Darrell Davis KT4WX
Mark Erbaugh