RTK Corrections unavailable when using RTK Express

[divyansh2681]

Subject of the issue

Describe your issue here. If you reference a datasheet please specify which one and in which section (ie, the protocol manual, section 5.1.2). Additionally, screenshots are easy to paste into github.

Your workbench

• What development board or microcontroller are you using? ESP32
• What version of hardware or breakout board are you using? ESP32
• How is the breakout board wired to your microcontroller? I2C
• How is everything being powered? MicroUSB
• Are there any additional details that may help us help you?

Steps to reproduce

Tell us how to reproduce this issue. Please post stripped down example code demonstrating your issue.

#include <SparkFun_u-blox_GNSS_v3.h> 
UBX_NAV_STATUS_data_t checkRTKstatus;
Serial.println(checkRTKstatus.fixStat.bits.diffCorr);

Expected behavior

Tell us what should happen Since I have connected the RTK Express to the GPS and powered it on, I should be receiving the RTK Corrections. But when I check the value of diffCorr variable (https://github.com/sparkfun/SparkFun_u-blox_GNSS_v3/blob/05eea9878f1e91575781d86b82642847fccce2cf/src/u-blox_structs.h#L189C9-L189C9), I always get 0.

Actual behavior

Tell us what happens instead The value of diffCorr should be 1 when RTK Corrections are available.

[PaulZC]

Hi Divyansh (@divyansh2681 ),

I have had a quick look at the source code and everything seems OK there. So I think there must be another reason why diffCorr is not changing state.

Please tell us more about how you have connected the RTK Express to the GPS:

• Which GPS are you using? Is it RTK-capable?
• How are the two connected? Which port on the GPS are you using to receive the corrections?
• Have you checked your wiring? TX->RX, GND->GND?
• Have you confirmed that the Express is outputting corrections? Are the internal switches set correctly?
• Are they both using the same baud rate?
• Does the GPS port have RTCM-In enabled?

Please attach photos here showing the wiring.

Best wishes, Paul

[divyansh2681]

Hi Divyansh (@divyansh2681 ),

I have had a quick look at the source code and everything seems OK there. So I think there must be another reason why diffCorr is not changing state.

Please tell us more about how you have connected the RTK Express to the GPS:

• Which GPS are you using? Is it RTK-capable?
• How are the two connected? Which port on the GPS are you using to receive the corrections?
• Have you checked your wiring? TX->RX, GND->GND?
• Have you confirmed that the Express is outputting corrections? Are the internal switches set correctly?
• Are they both using the same baud rate?
• Does the GPS port have RTCM-In enabled?

Please attach photos here showing the wiring.

Best wishes, Paul

Thank you for the response, Paul.

Here are the answers to your questions:

• Which GPS are you using? Is it RTK-capable https://www.amazon.com/gp/product/B0B9TTSN2V/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

• How are the two connected? Which port on the GPS are you using to receive the corrections? The RTK Express in Base Station mode is connected to the GPS using 2 telemetry radios

• Have you checked your wiring? TX->RX, GND->GND? I did check the SCL/SDA pins.

• Have you confirmed that the Express is outputting corrections? Are the internal switches set correctly? I confirmed that it says transmitting, and that the green light is solid while the red light is blinking

• Are they both using the same baud rate? Both radios are using the same frequency 915MHz

• Does the GPS port have RTCM-In enabled? I am not sure what this thing means. I will look into the RTCM examples and figure this out.

[PaulZC]

Hi Divyansh (@divyansh2681 ),

I can't see clearly from your first photo, the cable goes out of shot, but it looks like you have the Radio connected to the GPS-RTK USB port using a USB cable? That is not going to work. You need to provide the Radio with power and connect its TX pin to UART1 RX or UART2 RX on the GPS-RTK.

Please see this tutorial: https://learn.sparkfun.com/tutorials/setting-up-a-rover-base-rtk-system#rover-setup

Scroll down to: https://cdn.sparkfun.com/assets/learn_tutorials/1/3/6/2/Radio_attached_to_ZED-F9P.jpg

I am going to close this because this is an issue with your hardware connections, not an issue with this library. If you need more help, please ask a question on our GPS Forum: https://forum.sparkfun.com/viewforum.php?f=116

Best wishes, Paul

[divyansh2681]

Thank you for your help Paul.