---
title: "Test a Modbus reading in Chart’nX: result and unavailable test"
description: Test a Modbus register reading from Chart’nX, check the value received and fix a grayed-out test or a gateway that does not respond to the read.
canonical: https://wiki.can-nx.com/en/guides/chart-modbus-test/
language: en
product: Chart’nX
audience:
  - administrateur
  - installateur
context: "Chart’nX energy or water generator: Modbus catalog and configuration form"
---

# Test a Modbus reading in Chart’nX: result and unavailable test

Context: Chart’nX energy or water generator: Modbus catalog and configuration form

**Test read** requests a reading of the register from the installation’s gateway, from the Chart’nX Modbus catalog. You check that a configuration responds and that its value is consistent before using it in a dashboard. If the test is unavailable, the message displayed tells you what to do.

Intended for administrators and installers.

## Before you start

- Know the expected measurement.
- Have the correct device parameters: IP address, port, unit ID, register and advanced settings.

## Run a reading test

1. Open the [Modbus catalog](https://wiki.can-nx.com/en/guides/chart-modbus-catalog/), **Active**, then expand the gateway. You can also test from the **Test** section of the [configuration form](https://wiki.can-nx.com/en/guides/chart-modbus-config/), after filling in its parameters.
2. On the row you want, click **Test read**. The button changes to **Reading…**.
3. Wait for the result. A response shows the value and the time it was received. Without a response within the test time limit, the message is **No response from the gateway**.

## Check the result

Compare the value received with the expected measurement and the device documentation. A received value shows that the reading succeeds; also check the unit, the scale and the historization in the dashboard.

- Inconsistent value: check the data type, the length, the swaps and the scale factor against the manufacturer’s parameters.
- Difference between the reading and the chart: also check the unit, the factor, the indexed/non-indexed mode and the dashboard period according to [the meter troubleshooting](https://wiki.can-nx.com/en/guides/chart-meter-help/).

## Understand an unavailable test

| Message displayed | Action |
| --- | --- |
| **Gateway is connecting — test from the catalog once it is online.** | Finish the necessary creation, return to the catalog and try again once the gateway is available. Do not create a second gateway to work around this message. |
| **Gateway disabled — enable it to run a test.** | Check with the person responsible for the installation whether this deactivation is intentional. [Enabling the gateway](https://wiki.can-nx.com/en/guides/chart-modbus-gateway/) affects its configurations, not just this test. |
| **No matching gateway in this project — test unavailable.** | Check the project, the association with the Can’nX gateway and the catalog badges. If the correct association is not known, contact support. |
| **This configuration uses a legacy format — re-save it from the edit form before testing.** | Open **Edit configuration**, check the known parameters, click **Save**, then test again. If the expected values are missing, ask the installer or support for them. |

## Troubleshooting

For **No response from the gateway**:

1. First check that you are testing the right configuration and the right gateway.
2. Then have the installer check the IP address, the port, the unit ID, the register and the advanced settings against the installation information.

This message alone does not prove a hardware failure. Avoid a series of address or coefficient changes: if these checks do not succeed, contact support@can-nx.com with the product, the project, the configuration name, the message or value observed, the test time and the checks already made. Do not send any password or key.

For a measurement missing from the charts despite a successful read, or other Modbus questions, see the [Chart’nX Modbus FAQ](https://wiki.can-nx.com/en/guides/chart-modbus-faq/).

French labels: **Tester la lecture**.