WTF, this is new out of the bag.
Internal GPS Mod Tech Support/Q&A
- Thread starter jonwienke
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I had a batch of 5 of them emit smoke right out of the bag immediately on first power-up.
Every.
Single.
One.
The supplier sent me a batch of replacements, and every one of them was good. And they all had the exact same lot number markings as the smokers.
Your best bet is to order in bulk (5+ units) from multiple vendors to get a variety of lots/batches so that some of them will work. Did I mention that I hate the MAX3232??
Every.
Single.
One.
The supplier sent me a batch of replacements, and every one of them was good. And they all had the exact same lot number markings as the smokers.
Your best bet is to order in bulk (5+ units) from multiple vendors to get a variety of lots/batches so that some of them will work. Did I mention that I hate the MAX3232??
I think I may have figured out why this didn't work. The 436 UART chip (a TRS3221E variant) has an INVALID output that signals when the chip is receiving a valid RS-232 input signal. The output is high when a valid RS-232 input is being received, and is low when no valid RS-232 input is detected. If the scanner uses the INVALID output of the UART to ignore spurious serial data, then directly connecting a GPS TTL output to the UART output trace will not work unless you also jumper the INVALID output to VCC from the GPS to let the scanner know that the serial data on the UART output trace is good. If you don't, INVALID will be low because the UART isn't seeing any valid RS-232 input, and TTL output data will always be ignored.
If the HomePatrol uses the same or similar UART chip to convert RS-232 to TTL, then that's why direct TTL connection didn't work.
That's interesting. The HomePatrol uses a Sipex 3223EEY. I'll have to take a look at the datasheet again. I grabbed a known good 232 adapter and it still doesn't work so something strange is going on. (using the 232 input of course). I'm still trying to find my external GPS setup to test the radio for known good GPS operation.
The STATUS output of that chip (pin 11 or pin 21, depending on variant) has the same functionality as the INVALID output of the TRS3221E--high when a valid RS-232 input is detected, low otherwise. Check out the table at the top of page 16 of the datasheet:
SP3223 pdf, SP3223 description, SP3223 datasheets, SP3223 view ::: ALLDATASHEET :::
SP3223 pdf, SP3223 description, SP3223 datasheets, SP3223 view ::: ALLDATASHEET :::
Ok, but why would a UBLOX work and this not? Is it the difference in the data formatting?
No. They all use NMEA sentences, so if you have the baud rate right, and all the status lines set correctly, it should work.
When you're bypassing the scanner UART, it's not detecting a valid RS-232 input, and the status output from the scanner UART will be low, which will cause the scanner to ignore GPS input even if it's valid and all other settings match. You have to connect the GPS TTL output to the UART TTL output trace, and simultaneously jumper the UART status output to Vcc to force the scanner to recognize the TTL direct connection. Otherwise the TTL direct connection will not work.
I'm guessing you fried something in the scanner UART chip when you connected the GPS TTL output in parallel with the scanner UART TTL output, and now the scanner UART output isn't working right. That would explain why a RS-232 input is no longer making it through the scanner UART.
But it's also possible the MAX3232 module is being cranky.
Trace the serial data signal with an o-scope and see how far it's actually getting. Start at the GPS output, and then check the MAX3232 module input and output, then check the scanner UART input and output. It's the only way to know for sure where the fault is.
When you're bypassing the scanner UART, it's not detecting a valid RS-232 input, and the status output from the scanner UART will be low, which will cause the scanner to ignore GPS input even if it's valid and all other settings match. You have to connect the GPS TTL output to the UART TTL output trace, and simultaneously jumper the UART status output to Vcc to force the scanner to recognize the TTL direct connection. Otherwise the TTL direct connection will not work.
I'm guessing you fried something in the scanner UART chip when you connected the GPS TTL output in parallel with the scanner UART TTL output, and now the scanner UART output isn't working right. That would explain why a RS-232 input is no longer making it through the scanner UART.
But it's also possible the MAX3232 module is being cranky.
Trace the serial data signal with an o-scope and see how far it's actually getting. Start at the GPS output, and then check the MAX3232 module input and output, then check the scanner UART input and output. It's the only way to know for sure where the fault is.
Ah, I see. I thought you meant it was looking for malformed data packets which would be strange for a UART. I'll probably just hot air the UART off and go right to 3.3 or get another chip and replace it.
I can't imagine why applying 3.3 to a 3.3 line would toast it but it's sounding like that's the issue. Thanks for the insight.
This only happens when trying to do a conversion for someone else. All my stuff was plug and play. No good deed and all that...
I can't imagine why applying 3.3 to a 3.3 line would toast it but it's sounding like that's the issue. Thanks for the insight.
This only happens when trying to do a conversion for someone else. All my stuff was plug and play. No good deed and all that...
I recently had this mod done on my 436, and the gps works great! Fast and professional! Good communication and everything works great. Although I also had C1 installed, I have not seen very much improvement in reception. But when I use the roof mounted antenna in the car, it works great!
Thanks again Jonwienke!
Sent from my iPhone using Tapatalk
Thanks again Jonwienke!
Sent from my iPhone using Tapatalk
You're welcome.
The benefit of C1 install varies by unit; some scanners generate more battery compartment noise than others without it. C1 also makes the most difference when using a short SMA antenna like the factory duck. The range of the noise is very short, and moving the body of the antenna away from the scanner even an inch or so (which happens when you install the BNC adapter and use an antenna with a BNC connector) will reduce the interfering effect of the noise significantly. Using a longer antenna has the same effect; more of the antenna body is farther from the noise source than when using a short antenna. So if you normally run the Diamond RH77CA antenna, which is longer than the factory duck, and uses a BNC connector, not having C1 may have very little effect on reception. If you use an external antenna connected via a length of coax, having or not having C1 will have no impact on reception. But if you use the factory antenna, or something similar, not having C1 can have a significant negative effect on reception.
Anyway, I'm glad the mod is working well for you, and please do not hesitate to contact me if you have any issues or questions.
The benefit of C1 install varies by unit; some scanners generate more battery compartment noise than others without it. C1 also makes the most difference when using a short SMA antenna like the factory duck. The range of the noise is very short, and moving the body of the antenna away from the scanner even an inch or so (which happens when you install the BNC adapter and use an antenna with a BNC connector) will reduce the interfering effect of the noise significantly. Using a longer antenna has the same effect; more of the antenna body is farther from the noise source than when using a short antenna. So if you normally run the Diamond RH77CA antenna, which is longer than the factory duck, and uses a BNC connector, not having C1 may have very little effect on reception. If you use an external antenna connected via a length of coax, having or not having C1 will have no impact on reception. But if you use the factory antenna, or something similar, not having C1 can have a significant negative effect on reception.
Anyway, I'm glad the mod is working well for you, and please do not hesitate to contact me if you have any issues or questions.
Nope. Still trying to find my Uniden cable so I can verify the radio actually works with external regular input.
I don't see why it's not working. It makes no sense.
The problem arises when one output is sending 3.3V, and the other is sending 0V. If these outputs are connected together, you have a 3.3V power supply that is being shorted out. Unless both outputs have short circuit protection, something is going to fry.
Put an oscilloscope on the scanner UART output pin, and see if it is showing data (rapidly fluctuating between 0V and 3.3V), or if it is stuck at 0V or 3.3V. Use 20-50ms/division for your x unit, with a trigger threshold of 1-2V and triggering when input drops below the threshold. A normal multimeter won't react fast enough to give you a good reading if serial data is active.
If your scope supports multiple inputs, connect the second input to the scanner UART STATUS pin to see if it is indicating valid data going to the scanner when the scanner UART is getting good RS-232 input.
You want me to take a look at it?
Makes sense. I'll dig into it again and might hit you up about it if I keep having issues. Thanks
Did my suggestion to supply the ATGM336H GPS with 5V work? The MAX3232 will also handle 5V power input.
I've been out of town all weekend so haven't had time to try it yet unfortunately.
Any progress?
I did some testing, and my ATGM336H will run reliably with a MAX3232 starting at about 2.75V. Anything lower than that, and it starts having trouble getting a satellite lock, or simply outputs nothing. So 3.3V should be fine as a power supply voltage for both the GPS and the MAX3232.
I did some testing, and my ATGM336H will run reliably with a MAX3232 starting at about 2.75V. Anything lower than that, and it starts having trouble getting a satellite lock, or simply outputs nothing. So 3.3V should be fine as a power supply voltage for both the GPS and the MAX3232.
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I tried 5 volts and then also tried a level converter feeding 3.3 on the GPS side and 5 on the other side then fed that to the 232 adapter. Nothing works. I'm at a total loss here. It's as if the radio can't understand the info it's transmitting.
The data from the GPS appeared legit when probed with the logic analyzer.
The radio can understand a regular external GPS input using a puck GPS to the side plug.
The GPS gets a lock just fine and is blinking so it's not that.
I've tried several baud rates just to be sure but kept it on 9600.
The logic analyzer auto identified 9600 and decoded usable data at 9600 so that has to be correct.
I'm completely baffled at it at this point.
The data from the GPS appeared legit when probed with the logic analyzer.
The radio can understand a regular external GPS input using a puck GPS to the side plug.
The GPS gets a lock just fine and is blinking so it's not that.
I've tried several baud rates just to be sure but kept it on 9600.
The logic analyzer auto identified 9600 and decoded usable data at 9600 so that has to be correct.
I'm completely baffled at it at this point.
The TTL side of the SIPEX?
OK
OK
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