EVK-X20P: UBX-RXM-RAWX stops after ~2–3 minutes while NAV/SFRBX continue

Wireless and IoT RF and Wireless
1

We are experiencing a repeatable UBX-RXM-RAWX output failure on one EVK-X20P and would appreciate advice on whether this could be a firmware issue or defective hardware.

Setup

  • EVK-X20P-00 / ZED-X20P

  • Hardware: 000B0000

  • Firmware: HPG 2.02 (43e74c)

  • Protocol: 50.10

  • Connection: EVK USB-C to Linux/Raspberry Pi (/dev/ttyACM0)

  • Measurement rate: 2 Hz

  • UBX-RXM-RAWX and UBX-RXM-SFRBX enabled

  • Supplied active all-band EVK antenna

We use essentially the same configuration procedure on three EVK-X20P units, but only this unit consistently shows the problem.

Failure

After a power cycle, RAWX starts normally.

Latest capture:

  • 296 consecutive RAWX messages

  • Exactly 2.0000 Hz

  • 100% of intervals = 0.500 s

  • Continuous RAWX span = 147.5 s

  • No missing epochs before the failure

  • Populated RAWX messages are approximately 2.4–2.9 kB

  • After 147.5 s, RAWX stops completely and does not resume

A previous capture showed the same behavior after 271 RAWX messages / 135 s, so the cutoff is repeatable but not at an identical elapsed time.

Importantly, the receiver itself continues operating after RAWX stops:

  • UBX-RXM-SFRBX continues

  • UBX-NAV-PVT and other NAV messages continue

  • Receiver maintains a 3D fix with ~27–28 satellites

  • No USB disconnect occurs

  • The host continues receiving valid UBX messages

Immediately after RAWX stops, the RAM configuration still reports:

CFG-MSGOUT-UBX_RXM_RAWX_USB = 1
CFG-MSGOUT-UBX_RXM_SFRBX_USB = 1
CFG-RATE-MEAS = 500
CFG-RATE-NAV = 1

Rewriting CFG-MSGOUT-UBX_RXM_RAWX_USB = 1 does not restore RAWX. Restarting the host-side logger also does not restore it. A power cycle reliably restores RAWX, but only temporarily.

We have also reset/restarted the EVK and reapplied the configuration, but the behavior remains.

Important comparison

There is a strong dependency on whether RAWX contains actual observations.

Without an antenna connected:

  • RAWX contains numMeas = 0

  • Payload is only 16 bytes

  • Receiver ran for one full hour

  • Exactly 7,200 RAWX messages at 2 Hz

  • No interruption

With the supplied active antenna outdoors:

  • Approximately 76–90 observations per RAWX epoch

  • RAWX payload approximately 2.4–2.9 kB

  • RAWX stops after roughly 2–3 minutes

  • Other UBX messages and navigation continue normally

This makes us suspect an issue related to populated RAWX generation/output rather than a general USB or receiver failure.

Questions

  1. Is this a known issue with HPG 2.02 on ZED-X20P / hardware 000B0000?

  2. Is there a newer or recommended firmware version for this hardware?

  3. For the EVK USB-C connection, should RAWX output be controlled by the *_USB CFG-MSGOUT keys, or should *_UART1 keys be used?

  4. Are there diagnostic messages you recommend capturing around the failure, such as MON-TXBUF, MON-HW, MON-RF, or MON-MSGPP?

  5. Is there a supported command/reset that can restart RAWX generation without power-cycling the EVK?

  6. Given that the same configuration is used on three EVK-X20P units and only this unit consistently fails, could this indicate a defective receiver/evaluation kit?

We can provide the original binary UBX captures from both the failing outdoor test and the one-hour no-antenna test, complete MON-VER output, configuration dumps, and host-side logs.

2

Hello,

Welcome to the TechForum!

We are looking into this issue, if you have any other details, please add them to this.

Thank you
Ryan

3

Thank you for your answer. Currently I handed over the X20P to a colleague of mine. The X2-P is connected to a Raspberry Pi 3B+ and only next week I will have access again to the RP (remotely) and can provide additional information. If you want… I can provide the configuration script I use to set up the X20P.

configure_zed_x20p_usb_raw_output.py (12.0 KB)

check_ubx_hz_health.py (13.1 KB)

  • configure_zed_x20p_usb_raw_output.py: enables UBX-RXM-RAWX and UBX-RXM-SFRBX on USB and sets the measurement rate.

  • log_gnss.py: records the raw byte stream from the receiver without filtering.

  • check_ubx_hz_health.py: checks RAWX cadence and reports if RAWX disappears while other UBX traffic continues.

Please run the same sequence twice: once with the antenna connected outdoors, and once with no antenna connected. On our failing unit, RAWX stops after about 2 to 3 minutes only when RAWX contains real observations.

  1. Install ubxtool if needed

sudo apt install gpsd-clients

  1. Configure the receiver for RAWX/SFRBX on USB at 2 Hz

python3 configure_zed_x20p_usb_raw_output.py --device /dev/ttyACM0 --hz 2 --verify-persistent

  1. Power-cycle the receiver

  2. Log the raw UBX stream for 10 minutes

python3 log_gnss.py --device /dev/ttyACM0 --output x20p_test.ubx --duration 600

  1. Analyze whether RAWX stayed continuous

python3 check_ubx_hz_health.py x20p_test*.ubx --expected-hz 2

he next message is the script for collecting the data.

4

log_gnss.py (2.4 KB)

This could not be sent in the previous message.

5

This strongly suggests a RAWX processing or buffering issue. Populated measurements trigger failure after several minutes. Zero-measurement RAWX runs continuously for one hour. USB transport and navigation remain functional afterward. Compare working and failing units using MON diagnostics. Check MON-TXBUF, MON-MSGPP, MON-HW, and MON-RF.