NTP GPS
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So I tried connecting to my MC7700 Wireless which has GPS. I set autostart on the unit and I am unable to get any other the ports to work. NMEA COM7 worked on my PC and spit out lots of data so I would think the pfsense could see this also.
Do I need to restart after selecting a different com port on the NTP GPS settings?
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Got this fixed. Now just cannot seem to get GPS data for NTP to work. Also not sure what GPS is used in the sierra wireless. I tried the following interfaces…
Not sure if I have to wait or restart NTP after evey try?
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That's out of my scope, sorry.
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So I reached out to pcengines and they are telling me even that port will not work (COM2).
pcengines:
The DB9 connector of the serial port does not have any power pins. It's a regular RS232.
COM2 is on the 5 pin header J3. The part number of the 5 pin header is 640456-5, see https://www.digikey.ch/product-detail/de/te-connectivity-amp-connectors/640456-5/A19471-ND/259011 and it's mating counter parts.Me:
So Com 2 has power pin? Pin 5 5V and pin 1 3v?
pcengines:
Correct, J3 has 5V and 3.3V. Please be aware the RX/TX expect TTL level signals, not +/-12V RS232 signal levels.
Me:
I am looking at this for a serial connected GPS unit which requires 3v or 5v
https://www.aliexpress.com/item/Industrial-control-applications-RS232-protocol-output-UBLOX-6010-GPS-chip-design-DB9-connector-STOTON-GPS-receiver/32747390533.html
Will this work with that?
pcengines:
No, this will not work. It will not work on the DB9 connector COM1, because pin 9 has no power and it will not work on COM2, because the signal levels do not correspond.
I guess you want GPS for for getting position data? Other need the GPS signal for the exact timing signal it provides, but that is not possible with the module you suggested.
For positioning I would try one or more of these modules:
https://www.aliexpress.com/item/Free-Shipping-USB-GPS-Receiver-Ublox-7020-gps-chip-GPS-Antenna-G-Mouse-replace-globalsat-BU/32816622596.html
https://www.aliexpress.com/item/GPS-receiver-USB-driver-ublox-G7020-waterproof-built-in-FLASH-BT-708-replace-globalsat-BU-353S4/32818403478.html
https://www.aliexpress.com/item/NEW-UB-702-GPS-receiver-USB-module-antenna-ublox7020-CHIP-magnetic-waterproof-replace-globalsat-BU-353S4/32815397287.html
Me:
I need GPS for NTP Timing. I don't need milisecond accuracy though. What do you mean by signal levels do not correspond? Thanks! I am also using pfsense on the board.
pcengines:
The voltage of RS232 signals is +/-12V. The voltage of TTL signals is 0V/3V. COM1 is RS232 and has +/-12V levels, COM2 has 0V/3V levels.
Is is capable of any baud rate up to 1M.
For NTP you need a different module. -
That's easy. Take a max232 and convert the levels.
But I don't know how good you are at soldering. Would be a 10min task for me…PS: I don't know if those USB receivers are supported in FreeBSD. Next problem.
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Last time I soldered something was….never ;D Maybe time to learn!
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Or…..
https://www.startech.com/Cards-Adapters/Serial-Cards-Adapters/rs-232-to-ttl-signal-converter~IC232TTL
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Except for the price! That's ridiculous, parts cost is ~0.80 €/$
Technically it is correct. -
So I got the MC7700 to work for GPS but not for PPS. Looks like it cannot use PPS for this function. The question then is what is the accuracy of the GPS. I don't need milisecond accuracy. It can be give or take 5 minutes for my purpose.
I am waiting for response from China on a GPS unit that can do TTL, just not sure of PPS capable. PDF makes a reference to PPS.
Chipset used says it is PPS capabale Page 16
https://tinyurl.com/ybma6s6c
https://www.aliexpress.com/item/SKYLAB-RS232-USB-UART-TTL-protocol-DB9-USB-micro-fit-3-0-connector-GPS-Receiver-SKM55/32746957174.html Unit price is 22.44
http://www.skylab.com.cn/uploadfile/Download/201507071212151510.pdf
Possible to get unit with audio jack. 4 Pin See Pic
Then I would only need the SKM55 with 4 pin audio (TTL) see pic.
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Based on what I have found GPS without PPS provides basically the same type of time as would an NTP over a broadband connection. Basically 500 ms would be completely acceptable I would think for most applications.
https://superuser.com/questions/849526/gps-without-pps-vs-gps-with-pps-vs-ntp
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Hi…i am a new user here. As per my knowledge a punch out tool only makes sense for dozens of devices to modify.Just drill a hole and use a regular, round 3-conductor cable for your serial port. All you need is Gnd, TX & RX anyway. 1m of regular microphone cable from your local music store will do and is durable and solid.
