DMX Analyzer

This firmware was designed more for "DMX freaks" than for ordinary users. With the help of the analyzer, the signal of DMX consoles or PC interfaces can be evaluated and checked for compliance with the current standards.

In addition, the analyzer can transmit various reference signals in order to detect weak points in receivers such as dimmer packs or moving lights.

The analyzer consists of a DMX Transceiver and a 2x16 char Text-LCD (HD44780 compatible). Three push buttons are used as user interface.

DMX Transceiver (Rev. 3.2)

With this module, DMX data can be sent and received. However, due to using a microcontroller, this circuit is not ideal for beginners.

The Transceiver is suitable for bidirectional communication (e.g. RDM according to ANSI E1.20) due to the complete connection of the RS485 converter.

Industrial-quality circuit boards are available in the shop.

part list

As you can see, the circuit is quite simple: All the magic happens in firmware within the MCU (IC1). It is transferred to IC1 via the "ISP"port. The start address and special options (if any) are set via ADR. The LEDs serve as status indicators. The voltage regulator IC3 ensures a stable operating voltage of 5V. Q1 and C1,2 are needed for an operating frequency of 8MHz. The RS485 converter IC2 allows the MCU to communicate with the DMX universe. With the help of "Spare", various firmware options can be jumpered. Via A-Input, an analogue threshold value (e.g. for thermal protection) can be read.

A supply voltage between 9V and 12V dc is connected to PWR. The DMX Transceiver itself requires <300mA. When selecting the power supply, all loads must be taken into account.

The transceiver is connected to the DMX bus as shown in the next diagram:

Attention: Pin 3 of the XLR connectors is connected to the middle pin of the PCB connector!

Instructions for programming and selection of clock sources can be found under 'Resources'.

After changing the clock source, the Analyzer firmware can be transferred to the DMX Transceiver.

LC-Display (HD44780 compatible)

The LCD is connected to the output of the Transceiver using the following table. The pin assignment of the LCD can be found in its data sheet.

Push buttons

The analyzer is controlled by three buttons that pull the SPARE inputs to GND: 

How it works

DMX Timing

In this mode, the timing of the incoming DMX frames is measured. A new frame is indicated by a Break, in order to synchronise all receivers. This is followed by a Mark After Break to clearly distinguish the break from the subsequent start byte. After the start byte the individual channels are transmitted. Between individual channels, many transmitters wait a few microseconds in order to give poorly designed receivers time to process data. This delay is called an inter byte gap or inter slot time. According to the standard E1.20 the following timing is permissible:

Break:  176µs - 352µs
MAB:    12µs   - 88µs
IB-Gap: <32µs

Universe State

In this mode, the size of the universe and the refresh and error rates are measured. The refresh rate should be above 20Hz. A maximum of 512 channels are allowed. If a break occurs and the following start byte is neither 0x00 (DMX) nor 0xCC (RDM message), this is considered an error.

DMX Overview

10 consecutive DMX channels are displayed as a bargraph. The Up/Down buttons can be used to select the section being viewed.

DMX Input

The values of two consecutive DMX channels are displayed. The channels can be selected with the Up/Down buttons.

DMX Output Slow

512 channels are faded up and down. The transmission is slow with a very long break and inter byte gaps.

DMX Output Fast

64 channels are faded up and down. The output is very fast with minimum allowable break time and no inter byte gaps.

DMX Output Val

512 channels with the set value are transmitted in slow mode.