When working with Digi PKG (Boxed) Modems, there are some common troubleshooting steps that you can perform to help diagnose the source of the problem you are having. These are the same questions that support will ask when troubleshooting a communication issue:
Are you able to connect to the radio with X-CTU?
The Digi X-CTU software allows you to configure and test the radio. To determine if your PC can communicate to the radio, click the Test/Query button in the PC Settings tab of X-CTU. You can also read the configuration settings of the radio by going to the Modem Configuration tab and clicking “read”. If you are unable to perform either of these steps, it could be a baud rate mismatch between your computer and the radio, or possibly a communication fault with the PC.
Some USB-to-serial adapters are simply not compatible with Digi equipment. If possible, connect the radio to a computer with a physical COM port and test to ensure that your issue is not being caused by a faulty or incompatible USB-to-serial adapter.
To download X-CTU, please follow the following link: http://www.digi.com/xctu
The User's Guide for X-CTU can be found here: http://ftp1.digi.com/support/documentation/90001003.pdf
Are all radios on the network using the same hardware and the same firmware revision?
Newer firmware releases may introduce additional features, bug fixes, or protocol changes that may cause incompatibility with older firmware releases. All radios should be running the same version of firmware to ensure they communicate properly.
The hardware must also match. Even though several Digi radios use the same RF frequency and protocol technology, this does not necessarily mean that they are compatible with one another.
What is the baud rate the radios are operating at, and does your equipment also operate at that same baud rate?
All Digi RF radios operate at 9600 baud by default, if your equipment operates at a different baud rate than this, you will need to use X-CTU to configure the radios to match.
Note that some Digi radios have two different data rates, an RF (over-the-air) data rate, and an interface data rate. Because of additional overhead, the RF data rate must always be higher than the interface data rate.
Do the radios work when not connected to your equipment?
The easiest way of determining if the radios are working properly is to perform a range test. This tests two-way communication and ensures that there are no faults with the radios and no interference or range issues. A range test is generally performed with a loopback adapter and the X-CTU software. If you do not have a loopback adapter or have difficulties in performing this test, please contact Digi Support.
Does your equipment work without the radios (hard-wired)?
The Digi radios are effectively acting as a wire replacement; if a range test succeeds, then test your equipment by bypassing the radios all together. Test and ensure that your equipment works with your PC and software by connecting directly to the equipment with a serial cable (preferably the same cable that is used to connect to the radio.)
What is the status of the LED indicators?
When data is being transmitted, you should get a Tx indicator LED. When data is being received, you should see an Rx indicator. Some of our packaged radios have RSSI indicator LEDs, this shows a rough estimate of the signal strength of the last received packet.
You can easily test transmission and reception by using the Terminal tab of X-CTU. When you type a character into the terminal tab, the Tx LED should light on the transmitting radio, and the Rx LED should light on the receiving radio. If you swap the radios and perform the same test and do not get an Rx light, then there could be an addressing or hardware fault with the radio.
What power supply is being used?
If the power supply being used is under-powered, you will see reduced range. This is one of the more common issues when a battery pack or 9V battery is being used. Also, if the power supply is faulty the radio may work intermittently or the performance of the radio may be unreliable.
Please refer to your radio's user guide to determine if the power supply you are using meets the requirements of the radio, and test with a different supply if possible.
Are the DIP switch settings correct (if applicable)?
Some of Digi's RS-232/485 packaged radios include a row of DIP switches for simple out-of-the-box configuration. The settings that are loaded into the radio by setting these DIP switches only take effect when the radio is powered on. So every time the DIP switches are changed, you have to restart the radio before the change will take effect. Please refer to the User’s Guide to determine what DIP Switch settings you should be using.
Is the radio properly configured for the type of equipment you are connecting to?
For several of the Digi packaged radios, they are configured as RS-232 by default. If the equipment you are connecting to is RS-485, then you will need to modify the DIP switch settings to set the radio to operate in that mode.
Some equipment requires a null modem adapter be connected (null modem is only applicable for RS-232 equipment.) The null modem adapter simply swaps the Tx and Rx pins of the DB9 connector so that the proper polarity is used. If the radio was purchased with accessories, you should have been provided several of these adapters. The only way to determine if a piece of equipment requires a null modem adapter or not is by referencing the user's manual for the equipment that you are connecting to. A good rule of thumb is to test without the null modem adapter and if you are unable to communicate, add the null modem adapter and try again.
Is the application utilizing more than two radios and is your equipment capable of handling this type of configuration?
The Digi radios are capable of handling more than point-to-point operation. This includes point-to-multipoint, mesh network, and repeater modes. However, in simple transparent mode this type of configuration can easily become difficult to work with if your equipment or software is not designed to handle it. For example: if you have three remote nodes all sending data to a common base radio, it is likely that the data that is being sent will become mixed together and garbled. Some systems are designed to handle this type of scenario by having the remotes listen for data being transmitted and only sending when it is clear, or utilizing a type of software polling.
If your system is not designed for this type of operation but you still need to utilize more than two radios, there are frequently ways to work around the issue. Please contact Digi Support to discuss what options are available to you.
What type of antenna and RF cable is being used?
Make sure that the antenna you are using is properly connected and is the right type for the frequency and application you are using. We have an excellent article that discusses how to maximize range and general guidelines for antenna positioning. It can be found HERE.
If you need to run a long antenna cable to connect the antenna to the radio, ensure that it is the proper type for the frequency and distance that it is being run.
All RF cables add some loss to the system. For any given cable, the longer the cable the more signal will be lost over that cable. Because of this the length of the cable should be kept as short as possible. Often a longer serial cable can be used to minimize the length of the antenna cable. All RF cables have losses which are usually measured in dB of loss per 100 ft. Some common cables and losses are included in this table:
|Cable Type||Loss at 900 MHz|
Per 100ft (per 100m)
|Loss at 2.4 GHz|
Per 100ft (per 100m)
|RG-58||14.5 (47.4)||25.3 (83.2)||0.195 (4.95)|
|RG-174||25.9 (85.0)||44.4 (145.84)||0.100 (2.54)|
|RG-316||24.7 (81.0)||42.4 (139.0)||0.102 (2.59)|
|LMR-195||11.1 (36.5)||19.0 (62.4)||0.195 (4.95)|
|LMR-240||7.6 (24.8)||12.9 (42.4)||0.240 (6.10)|
|LMR-600||2.5 (8.2)||4.4 (14.5)||0.590 (14.99)|
What system protocol is being used, if any (Modbus, DF1, etc.)?
Some serial protocols require that data be transmitted and an acknowledgement received within a very short period, this is to ensure that the system is operating properly. With a wired connection, this will help identify problems, but with wireless, latency is introduced. Because the equipment expects the data to be sent with very tight timing, the added latency will cause the system to misidentify a fault, and it will usually report an error or not communicate at all.
Usually, there is a way to increase the response timeout in the system being used. There are very few ways of reducing the RF latency, so it is best to try to increase this timeout if possible.