MiniPlex-41 NMEA-0184 multiplexer Manual

Transcription

1 MiniPlex-41 NMEA-0184 multiplexer Manual MiniPlex-41, V1.0 Firmware V1.10 CustomWare, 2002

2 Introduction The MiniPlex-41 is a four-channel datamultiplexer, enabling the connection of multiple NMEA-0183 instruments to each other and a computer. Available are four NMEA inputs (listener-ports), tow NMEA outputs (talker-ports) and one RS-232 port. Specifications: Supply voltage: Current consumption: Inputs: Input resistance: Outputs: Buffers: NMEA Out1: NMEA Out2: Speed NMEA in: Speed NMEA1/RS-232 out: Speed NMEA2 out: Indicators: Dimensions: Housing: 8 20 V DC, protected against reversed polarity. 40 ma (70 ma max. with fully loaded talker ports). 4 x NMEA-183/RS-422, galvanically isolated. 1,5 kohm. 1 x RS-232, 2 x NMEA-183/RS buffers of 1500 characters (4 x NMEA, 1 x RS-232). Combined data from NMEA inputs. Combined data from NMEA and RS-232 inputs or only from RS-232 input Baud. 4800, 9600, 19200, or Baud Baud. Overflow and Data. 138 x 72 x 33 mm. Flame retardant ABS. Operation The MiniPlex-41 reads NMEA sentences from the listener ports and stores them in a buffer per port. When a complete sentence is received, it dumped to the talker ports and the RS-232 port. The buffers are dumped in a round-robin fashion, one sentence at a time, thus giving each listener port equal priority. Reception of new sentences continues during dumping, so no data is lost. The speed of the listener ports is fixed to 4800 Baud (= bits per second), which roughly equals 480 characters per second. When all listener ports receive data at this rate, the buffers will not be emptied in time and an overflow situation occurs. The red LED indicates this situation. When a buffer is full, a partially received sentence will be discarded, to ensure that the MiniPlex-41 only dumps complete and valid sentences. There are two ways to resolve this overflow situation: 1. Configure the instruments on the listener ports to send less data or with greater intervals. It is often possible to disable non-relevant sentences. 2. Increase the speed of the talker port and the RS-232 port on the MiniPlex-41. The maximum speed is Baud. From Baud and up (4 x 4800!) an overflow will never occur (only with Configuration 2 selected). The MiniPlex-41 has two talker ports, Out 1 and Out 2. All received sentences from the listener ports are available on talker port Out 1. Talker port Out 2 can be configured either to output all received sentences from the listener ports and the RS-232 port, or only sentences from the RS-232 port. 2

3 Connections NMEA Listener Ports The MiniPlex-41 has four listener ports, In 1 to In 4. Each listener port should be connected to one instrument only. These inputs are galvanically isolated as specified in the NMEA-0183 standard. Connect the a and b terminals of the listener port on the MiniPlex-41 to the a and b terminals of the talker port on the instrument. Other designations used are Data + and Data -. Some instruments have single ended talker ports, with only one data terminal. Connect this terminal to the a terminal on the MiniPlex-41, and connect the b terminal on the MiniPlex-41 with the instrument ground. NMEA Talker Ports Both talker ports can be connected to up to four instruments. Connect the a and b terminals of the talker port on the MiniPlex-41 to the a and b terminals of the listener port(s) on the instrument(s). Other designations used are Data + and Data -. Some instruments have single ended listener ports, with only one data terminal. Connect this terminal to the a terminal on the MiniPlex-41, and leave the b terminal on the MiniPlex-41 unconnected. Connect the Com terminal on the MiniPlex-41 with the instrument ground. RS-232 Computer Port The RS-232 port on the MiniPlex-41 can be connected directly with the serial port of a computer, as shown in the diagram below RxD TxD Com MiniPlex-41 terminals rear-view of 9-pin sub-d connector Power Supply The MiniPlex-41 operates from a DC supply voltage from 8 to 20V and is protected against reversed polarity. It is recommended to connect the MiniPlex-41 to the same power source or circuit breaker as the ships instruments and/or computer. 3

4 Configuration Various options can be configured on the MiniPlex-41, using a terminal program like ProComm or HyperTerminal. Commands are issued as control characters. Press the control-key on your keyboard first and while holding the control-key down, press the appropriate letter key. With these commands, the speed of the Rs-232 port and talker port Out 1 can be set, as well as the source of the data available on talker port Out 2. Commands Connect the MiniPlex-41 to the serial port of a computer and set the user terminal program to 4800 Baud, 8 data bits, 1 stop bit. Do not connect any instruments yet. Apply power to the MiniPlex-41 and check if the red and green LED s blink once. Issue a ctrl-i command, by pressing the control-key and de i key simultaneously. The following text should appear on your screen: MiniPlex-41 V1.0, Firmware V1.10, (C) CustomWare 2002 Speed: 4800 Baud Conf.1: NMEA Out2 = RS NMEA In Now the MiniPlex-41 can be configured with the following commands. Ctrl-a Stores the configuration settings in non-volatile memory. This saves the settings permanently during power down. Ctrl-b Change the communication speed (baud rate) of the RS-232 port and talker port Out 1. Every time you issue this command, the speed is cycled to the next higher value, thus selecting 4800, 9600, 19200, 38400, or Baud. The selected speed is shown on the screen. The setting is activated when you issue the ctrl-a command. On the screen, the message Settings saved appears, after which you have to adjust the settings of the terminal program to the selected speed, to be able to communicate again with the MiniPlex-41. Whenever you lost track of the speed setting, try to issue the ctrl-i command at different speed settings of your terminal program, until the aforementioned text appears on the screen. Ctrl-c This command determines which NMEA data is available on talker port Out 2. The selected option is displayed as shown below: or: Conf.1: NMEA Out2 = RS NMEA In Conf.2: NMEA Out2 = RS-232 The chosen option is effective immediately, but must be saved permanently with the ctrl-a command. This command does not affect talker port Out 1, this port only outputs data from the talker inputs. Ctrl-h This command resets the MiniPlex-41 to the factory configuration, which is 4800 Baud and Configuration 1. Ctrl-i Information command. Displays information about the hardware/software version and the current configuration settings. 4

5 Configuration 1 and 2 The selected configuration determines how the received NMEA data is handled by the MiniPlex-41. In 1 Buffer 1 NMEA In 2 In 3 Buffer 2 Buffer 3 RS-232 Out NMEA Out 1 In 4 Buffer 4 RS-232 In Buffer 5 NMEA Out 2 Configuration 1 The diagram above shows where the NMEA data is available in Configuration 1. The RS-232 port and talker port Out 1 transmit the data from the listener ports. Talker port Out 2 transmits data from the listener ports and the RS-232 port. The selection of Configuration 1 imposes a limitation on the speed of the RS-232 port. The speed of talker port 'Out 2' is fixed to 4800 baud, which equals 480 characters per second. In Configuration 1, the NMEA data is sent to both the RS-232 port and talker port 'Out 2' at the same time. Whatever speed is selected for the RS-232 port, it has to wait until talker port 'Out 2' has finished transmitting a character. The RS-232 port and this talker port will always output their data with the same character-rate, despite the difference in bit-rate. Configuration 2 does not have this limitation. In 1 Buffer 1 NMEA In 2 In 3 Buffer 2 Buffer 3 RS-232 Out NMEA Out 1 In 4 Buffer 4 RS-232 In Buffer 5 NMEA Out 2 Configuration 2 When Configuration 2 is selected, data is available according to the diagram above. The RS-232 port and talker port Out 1 transmit the data from the listener ports. Talker port Out 2 only transmits data from the RS-232 port. With an example, the effect of both configurations will be shown. First, Configuration 1 is selected. All NMEA sentences received from the instruments are available on the RS-232 port and talker port Out 2. This means that the laptop and the autohelm receive all sentences from the connected instruments. From the laptop, waypoints can be downloaded into the GPS and the autohelm can use all available information to steer the right course. If the autohelm should only respond to data from the laptop, select Configuration 2. The NMEA sentences from the connected instruments are now only available on the RS-232 port and thus only to the laptop. The only data available on talker port 'Out 2' is data from the laptop, which is 5

6 therefore the only source of data for the autohelm. Note that NMEA data from the connected instruments is always available on talker port 'Out 1', regardless of the selected configuration. Wind Compass In 1 In 2 RS-232 Laptop GPS In 3 Out 2 MiniPlex-41 Autohelm Factory Setting It is possible that a situation occurs where your computer or navigation software stops working, and you need to reconnect the instruments to keep your ship going. In such a case, the MiniPlex- 41 can be reset to its basic multiplexer function, running at 4800 Baud and Configuration 1. This reset is performed by connecting the TxD to the RxD terminal of the RS-232 port, while switching on the power. Indicators The MiniPlex-41 has two LED s. The green LED indicates the reception of valid NMEA data on the listener ports of the RS-232 port. The LED only blinks on valid NMEA sentences, that start with a $ and end with a LF character, thus indicating a proper connection and polarity of the connected instrument. In case of a reverse polarity, the green LED will not blink. The red LED indicates a buffer overflow, in case more data is coming in, than can be transmitted. When a buffer is full, a partially received sentence will be discarded, to ensure that the MiniPlex-41 only dumps complete and valid sentences. There are two ways to resolve this overflow situation: 1. Configure the instruments on the listener ports to send less data or with greater intervals. It is often possible to disable non-relevant sentences. 2. Increase the speed of the talker port and the RS-232 port on the MiniPlex-41. The maximum speed is Baud. From Baud and up (4 x 4800!) an overflow will never occur (only with Configuration 2 selected). Both LED s will blink once when the power is applied to the MiniPlex-41. When the red LED stays lit, a hardware error is found during execution of the self-test. Mounting The MiniPlex-41 is not waterproof. It should be mounted at a dry place, like behind the instrument panel, on a flat surface. 6

7 CustomWare Roggehullen WG Assen The Netherlands Tel.: Fax: web: info@customware.nl 7