MiniPlex-41USB NMEA-0183 multiplexer Manual

Transcription

1 MiniPlex-41USB NMEA-0183 multiplexer Manual MiniPlex-41USB, V1.0 Firmware V1.20 CustomWare, 2002

2 Introduction The MiniPlex-41USB is a four-channel datamultiplexer, enabling the connection of multiple NMEA instruments to each other and a computer. Available are four NMEA inputs (listener-ports), tow NMEA outputs (talker-ports) and one USB port. Specifications: Supply voltage: Current consumption: Inputs: Input resistance: Outputs: Buffers: NMEA Out1: NMEA Out2: Speed NMEA in: Speed NMEA1/USB out: Speed NMEA2 out: Indicators: Dimensions: Housing: 5V DC, from USB bus. 70 ma (100 ma max. with fully loaded talker ports). 4 x NMEA-183/RS-422, galvanically isolated. 1,5 kohm. 1 x USB, 2 x NMEA-183/RS buffers of 1500 characters (4 x NMEA, 1 x USB). Combined data from NMEA inputs. Combined data from NMEA and USB inputs or only from USB input Baud. 4800, 9600, 19200, or Baud Baud. Overflow and Data. 138 x 72 x 33 mm. Flame retardant ABS. Operation The MiniPlex-41USB reads NMEA sentences from the listener ports and stores them in a buffer. When a complete sentence is received, it is sent to the talker ports and the USB port. The buffers are emptied in a round-robin fashion, one sentence at a time, thus giving each listener port equal priority. Reception of new sentences continues during sending, 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-41USB only sends 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 USB port on the MiniPlex-41USB. The maximum speed is Baud. From Baud and up (4 x 4800!) an overflow will never occur (only with Configuration 2 selected). The MiniPlex-41USB 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 USB port, or only sentences from the USB port. 2

3 Connections NMEA Listener Ports The MiniPlex-41USB 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-41USB 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-41USB, and connect the b terminal on the MiniPlex- 41USB 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-41USB 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-41USB, and leave the b terminal on the MiniPlex- 41USB unconnected. Connect the Com terminal on the MiniPlex-41USB with the instrument ground. USB Port The MiniPlex-41USB can be connected directly with the USB port of a computer or a USB hub with the supplied cable. The first time the MiniPlex-41USB is connected, the computer will detect new hardware and ask for a driver disk. Insert the driver disk into the diskdrive and click OK. Follow the directions on the screen to complete the installation. Power Supply The MiniPlex-41USB is powered from the USB bus and does not need external power. When operation is required with the computer switched off, the MiniPlex-41USB can be powered from a USB hub with an external power connection. Driver Installation The MiniPlex-41USB needs a device driver for proper operation. When the MiniPlex-41USB is connected for the first time, Windows will detect new hardware and ask for a driver disk. Insert the supplied disk into the disk-drive and follow the instructions on your screen. The installed driver will provide a virtual serial port, which can be used by existing applications like any normal serial port. Through the System icon in the Control Panel, the settings of this port can be changed, as well as the port number. More than one MiniPlex-41USB can be connected at the same time. Every new unit will create a new virtual serial port. The number of this port will always be assigned to the same unit. Windows allows a maximum of 255 virtual serial ports. Not all software my be compatible however, with serial ports numbered above COM9. Many applications will only allow port numbers up to 4. When installing updated drivers, uninstall the original drivers first, with the Add/Remove Programs icon in the Control Panel. 3

4 Configuration Various options can be configured on the MiniPlex-41USB, using a terminal program like 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 serial port and talker port Out 1 can be set, as well as the source of the data available on talker port Out 2. Although this is a USB device, the MiniPlex-41USB still has a serial port which can be configured. This port is connected to talker port Out1 and the USB interface inside the unit. It is therefore still neccesary to match the communication speed of the MiniPlex-41USB to the speed of the virtual serial port. Commands Connect the MiniPlex-41USB to a computer and set the terminal program to 4800 Baud, 8 data bits, 1 stop bit. Do not connect any instruments yet. Apply power to the MiniPlex-41USB 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-41USB V1.0, Firmware V1.10, (C) CustomWare 2002 Speed: 4800 Baud Conf.1: NMEA Out2 = USB + NMEA In Now the MiniPlex-41USB 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 USB 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-41USB. 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 = USB + NMEA In Conf.2: NMEA Out2 = USB 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-41USB 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- 41USB. In 1 Buffer 1 NMEA In 2 In 3 Buffer 2 Buffer 3 USB Out NMEA Out 1 In 4 Buffer 4 USB In Buffer 5 NMEA Out 2 Configuration 1 The diagram above shows where the NMEA data is available in Configuration 1. The USB 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 USB port. The selection of Configuration 1 imposes a limitation on the speed of the USB 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 USB port and talker port 'Out 2' at the same time. Whatever speed is selected for the USB 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 USB Out NMEA Out 1 In 4 Buffer 4 USB In Buffer 5 NMEA Out 2 Configuration 2 When Configuration 2 is selected, data is available according to the diagram above. The USB port and talker port Out 1 transmit the data from the listener ports. Talker port Out 2 only transmits data from the USB 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 USB port and talker port Out 2. This means that the laptop and the autopilot receive all sentences from the connected instruments. From the laptop, waypoints can be downloaded into the GPS and the autopilot can use all available information to steer the right course. If the autopilot should only respond to data from the laptop, select Configuration 2. The NMEA sentences from the connected instruments are now only available on the USB port and thus only to 5

6 the laptop. The only data available on talker port 'Out 2' is data from the laptop, which is therefore the only source of data for the autopilot. 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 USB Laptop GPS In 3 Out 2 MiniPlex-41USB Autopilot Indicators The MiniPlex-41USB has two LED s. The green LED indicates the reception of valid NMEA data on the listener ports or the USB 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- 41USB 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 USB port on the MiniPlex-41USB. 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-41USB. When the red LED stays lit, a hardware error is found during execution of the self-test. Mounting The MiniPlex-41USB is not waterproof. It should be mounted at a dry place, like behind the instrument panel, on a flat surface. 6

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