Here 4 PPS

Here GPS
1

Hi guys,

I’m interested in testing the Here 4. I’ve read that there’s a PPS output but I’m wondering how can we get access to it?

Best regards,
Cedric

2

Bump on this! I see the breakout pin 10 has pps. Is this accessible and does it require special firmware?

3

Yes I saw that too @Andrew_Gregg ;).

So the first question is to know if by default the pps is available in that pin, and the second question is how to open the here 4 (I did not make any research on that) if we want to connect to the PPS. I have not bought any here4 yet, but I’ve seen it comes with a cable which has CAN and UART(I2C) output. So we we can open easily the here4 (what about the IP rating after opening) it would be fairly easy to modify the existing cable to connect to the PPS…

1 Like
4

@cedg507 The PPS signal is generated for every solution. You will need to open the Here4 to connect the adapter board. To open the Here4 ensure that you use non-metalic softer tools.
This is an experimental operation and any damage to the module in the process of opening is your responsibility. Saying that the best strategy is to start from the corners where the LEDs are and start prying the lid open. There are clips all round the case, you will need to circle through gently opening each clip.

Also note that with latest firmware Here4 publishes timesync message synchronised based on the PPS signal, and transmits the timestamp synchronised to GPS time.

5

@sidbh I need to change PPS Pulse length and mode, but I have some issues:

  1. Unfortunately I have lost PPS signal on PPS output after the software update of Here4 :frowning:
  2. Before the update I had default PPS signal on PPS output: mode-rising edge and pulse lenght-100ms.
  3. I couldn’t establish connection with u-center before the software update. I have successfully connected to u-center after the software update but now i don’t have PPS on PPS output (high state only regardless GPS FIX)
  4. After changing PPS parameters in u-center following the u-center manual (https://content.u-blox.com/sites/default/files/u-center_Userguide_UBX-13005250.pdf) they are not saved in the receiver.

Can you tell me how PPS signal can be restored on the PPS output of Here4 with custom parameters?

6

@BB8 Software automatically configures the PPS pin, but when you are in passthrough mode via Mission Planner to U-Center, the pin will not be configured, as it locks out the firmware from talking to GPS. I have verified the latest firmware seems to be setting up the PPS pin fine. Have you checked if PPS pin triggers show up couple of seconds after boot, without passthrough to u-center.

You can wait for ublox saving config show up on the DroneCAN panel like this

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after this I believe the pps config should stick.

7

@sidbh after the firmware update PPS signal looks like this:

WhatsApp Image 2024-08-13 at 11.55.43
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it is 200ms period, with 5us pulse lenght. When there is NO FIX it is only in high state. Before the firmware update on Here4 the PPS signal was 1s period with 100ms pulse length.

I checked the osciloscope signal on PPS output without connecting the autopilot to PC. Nothig changes regardles the connection to the Mission Planner.

I tried Here4 update again but nothing changed.

I try to change GPS parameters in u-center like this:

  1. In messages view I change Timepulse to Pulse Lenght 500ms.

    image
    image1706×1101 191 KB

  2. I click Send button

  3. TP message in left view changes to black from gray for a short time and then return to grey.

  4. In UBX-CFG-CFG I click Send with save current configuration

    image
    image1703×1101 211 KB

  5. CFG message in left view changes to black from gray for a short time and then return to grey.

  6. In Packet Console there is confirmation that the data is sent.

    image
    image964×406 114 KB

  7. I don’t get ublox saving config on the DroneCAN panel:

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    image1010×976 28.5 KB

  8. Nothing changes on PPS output.

Is there any possibility to restore factory default setings in Here4 or downgrade the firmware manually?

8

@BB8 the PPS output period is being configured by the firmware to be in sync with NAV solution which is 5Hz, this is used for better timekeeping. Changing this config in u-center will not do anything, as it will be reverted back to default config.

If you need to do custom config for PPS through u-center, you will need to disable PPS in the firmware. Set this to false, and build firmware GNSSPeriph-release/Here4/hwdef.dat at release · CubePilot/GNSSPeriph-release · GitHub.