What's the difference between the ZED-F9P and the ZED-X20P? a learn.sparkfun.com tutorial

Available online at: http://sfe.io/t4068

Contents

Introduction

The ZED-X20P is u-blox's GNSS receiver designed as a successor to the wildly popular ZED-X9P. It has improvements in accuracy, band reception, and power consumption. Here, we outline the key differences between our ZED-F9P and ZED-X20P breakout boards so you know exactly how to upgrade your projects to the newest technology.

Comparison of Features

u-blox provides the following table comparing key high-level differences between the features on the ZED-F9P and the ZED-X20P:

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We've also compiled the differences between the chips across more specific features:

Parameter ZED-F9P ZED-X20P
PPS Accuracy 30 ns 20 ns
Convergence Time < 10 s < 7 s
Max Velocity 500 m/s 300 m/s
Velocity Accuracy 0.05 m/s 0.03 m/s
Backup Battery Current 45 µA 32 µA
SW Backup Current 1400 µA (1.4 mA) 93 µA
Peak Current 130 mA 80 mA*
Acquisition Current 95 mA 68 mA*
Tracking Current 93 mA 64 mA*


Notes: u-blox has recently removed support for the GLONASS GNSS constellation. This is not accounted for in the listed current consumption of the ZED-X20P.

Hardware Changes

With the exclusions of the added JST connector and adjusted location of the BlueSMiRF header; the overall board dimensions, edge connectors and screw-hole locations, and PTH pin layout are exactly the same.


Allband GNSS RTK Breakout - ZED-X20P (Qwiic)
GPS-RTK-SMA Breakout - ZED-F9P (Qwiic)
GPS-RTK2 Board - ZED-F9P (Qwiic)


Antenna Connection

Connector Options

With the ZED-F9P we released two different boards with either a U.FL connector or an SMA connector to attach a GNSS antenna. With the ZED-X20P, we have released a single board with both options with a jumper to select the connector to be used.

SMA: The location of the SMA connector remains the same.

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U.FL: The U.FL connector’s location is slightly different by a couple millimeters. There was a hole in the board to pass a U.FL cable through.

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Notes: We did our best to maintain an impedance match between the two different connections. Users may experience a small shift in the signal’s impedance after altering their board. However, in our experience, the GNSS receiver was still functional after modifying the jumper and we didn’t really notice a degradation in performance.

Length of SMA Connector

We recently changed suppliers for our SMA connector, so users will eventually see a slightly longer SMA connector on future boards.

Old version: 6.3mm
New version: 8mm

BlueSMiRF Header Location

On the ZED-F9P boards, the BlueSMiRF PTH pins were located at the edge of the board. For the ZED-X20P, we have added a locking JST connector, in its place, to allow users to easily attach an RF transceiver. Therefore, the BlueSMiRF header was relocated to the interior of the board.

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Notes: The pin layout of the BlueSMiRF header remains the same; connecting to the UART2 interface of the GNSS receiver. On the ZED-X20P, we added a VSEL jumper for users to switch between either a 5V or 3.3V input/output voltage for the BlueSMiRF header.

Pin Functionality

Most of the pin functionality remains the same, with the exception of a single pin. The safeboot pin on the ZED-Z20P board was relocated to a test point and replaced with the enable pin for the RT9080 LDO.



ZED-F9P: Safeboot Pin
ZED-X20P: RT9080 Enable Pin


Notes: The SPI interface is enabled with the DSEL jumper for the ZED-F9P; meanwhile, for the ZED-X20P, it is enabled with the SPI jumper. The operation of these jumpers remains the same; only the name changed on the silkscreen. Similarly, the EVENT and INT pins are both external interrupt pins; only the name changed on the silkscreen.

UART Interface

Baud rate:

Notes: Default baud rate is 38400 bps. The ZED-F9P only supports the RTCM protocol up to v3.3

SPI Interface

Max transfer rate:

Max clock speed:

Notes: The transfer rate for the ZED-X20P is based on the load capacitance. SPI interface must be enabled by the jumper.

I2C Interface

The ZED-F9P only supported I2C fast-mode; while the ZED-X20P supports standard mode, fast mode, and fast mode plus.

Max bit rate:

USB Interface

While both boards provide a USB-C connection to the GNSS receiver, on the ZED-X20P we would advise users not to rely on this interface in their designs.

Notes: For the ZED-X20P, we broke out this interface as part of a preliminary design recommendation. However, u-blox has recently removed this interface from their latest datasheet. Therefore, we would recommend that users not integrate this interface into their future designs. Especially when it doesn’t support firmware updates.

Software Changes

Firmware Upgrade

As mentioned about the USB interface, above, it is only possible to perform firmware updates through the UART1 interface for the ZED-X20P.

Firmware upgrade through I2C (Qwiic) is possible, but is only for advanced users. You need (e.g.) a Thing Plus board running a sketch to convert USB UART to I2C. Then you need to run the u-blox ubxfwupdate.exe from the command line with some special settings.

u-center Application

One of the biggest changes between the two GNSS receivers is the u-center software application. u-blox recommends their new u-center 2 software application for any GNSS engine, generation 10 or later.

table showing differences between u-blox's u-center and u-center 2 products

The first difference between the two applications is that users will notice is a required user account for u-center 2. While users will need internet access to initially login, users will not need internet access or to login afterwards.

Beyond a new look and feel, the primary difference in functionality between the two applications is that the new generation 10 GNSS engines implement a new set/get method for the values in the configuration layers of the GNSS receiver. This is handled in the backend of the software application, but should be noted for any development purposes.

Some other notes to mention:

Notes: Nate has found that if users wish to continue using the original version of u-center (not u-center 2), they just need to use the generation 9 advanced configuration view. See Section 5.2.7 Generation 9 configuration view of this manual.

Arduino Library

With the introduction of the set/get method for configuration values for the gen 10 GNSS engines, our Arduino library got a new release (v3). The Arduino library should be mostly backwards compatible, with a few minor changes, see below for more information:


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