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[POTM] dAISy - A Simple AIS Receiver

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Overview dAISy (do AIS yourself) is a very simple AIS receiver that I developed from scratch. It is built around the Silicon Labs EZRadioPRO Si4362 receiver, using a Texas Instruments MSP430G2553 MC

Ain't she pretty?    

Good news for everyone having difficulties sourcing the Si4362 radio IC.   I verified that the transceiver Si4463 works with dAISy. This probably also applies to Si4460 and Si4461. Besides being mor

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Ok, Ok. Thanks gmtii (post 72 I will use...). There are...


pi@raspberrypi ~ $ ls /dev/ttyACM*
pi@raspberrypi ~ $ sudo lsusb
Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 001 Device 008: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Bus 001 Device 004: ID 0451:2046 Texas Instruments, Inc. TUSB2046 Hub
Bus 001 Device 005: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter
Bus 001 Device 006: ID 16d0:0b03 GrauTec
Bus 001 Device 007: ID 2047:0203 Texas Instruments
pi@raspberrypi ~ $ ls /dev/ttyUSB*
pi@raspberrypi ~ $

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Grrr! The VID/PID I bought from MCS Electronics seems to already be taken (GrauTec: 16d0:0b03).

-> Correction, it looks like someone added a GrauTec device with ID 16d0:054b to Linux, and then assumed that GrauTec also owns the VID, which is not the case.


In practice that shouldn't be an issue. Just go for the exposed ttyUSB0.

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  • 2 weeks later...

One of the most interesting aspects of selling your widget is seeing how other people use your product and what their requirements are.


dAISy was originally built for ship-geeks that are entertained for hours with MarineTraffic (like myself). I also broke out a few pins for tinkerers that want to connect dAISy to other widgets (again, like myself). Turns out, the majority of my customers are boat owners (unlike myself).


Boaters use dAISy to keep track of ships around them for navigation purposes, i.e. avoiding collisions. Free software called OpenCPN turns a laptop (or a RaspBerry Pi for the more geeky faction) into a chartplotter, a device that typically costs $500+. dAISy is connected via USB and provides real-time information about nearby ships. However, many boaters already have a traditional chartplotter and want to connect these with dAISy for AIS input.


Most chartplotters talk NMEA 0183, a serial standard compatible with RS-422. Unfortunately, that's not the same as the UART serial output of dAISy. Which leads to NMEA output as the 2nd most requested feature for dAISy (right after native WiFi*).


Electronic tinkerers can convert dAISy's TX output into a signal that works with some (most?) NMEA 0183 consumers using an NPN transistor and two resistors:


Exact resistor values don't matter that much, as their purpose is mostly to limit current. Slightly higher values should work as well.


Besides not being really NMEA/RS-422 compliant, requiring to solder obviously is a non-starter for the majority of my customers. So I decided to look for an integrated, more polished solution.


First step is implementing proper RS-422 driven from dAISy's serial output (TX). Luckily there's a chip for that. Well, there are many, but I settled for the TI UA9638.



As I didn't want to change dAISy's main PCB (NRE, the bane of mass production), I designed a PCB that screws to the backside of the existing enclosure. On the inside of the PCB is the RS-422 driver and a connector for a cable to the main PCB. The cable is soldered to existing breakout pads for TX, 5V and GND. Still on the inside, I also added a DC/DC converter so that dAISy optionally can be powered from the boat's 12V power system instead of USB. On the outside of the PCB is a beefy screw terminal to connect NMEA 0183 and 12V wiring.


Here is a picture of the first iteration I built today. The PCB on the left shows the inside, with DC/DC converter and related passives still unpopulated.



The NMEA 0183 output works as expected. I'm not sure yet about including the DC/DC converter in the final design. I'm worried that having a switching power supply inside the enclosure will introduce noise and interfere with the radio's performance.


I plan to add this or a similar design to my Tindie store early next year. In the meantime, any volunteers that have a chartplotter and dAISy and want to test the add-on should contact me.


*Besides being wireless, WiFi is popular because it's the only way to get real-time NMEA data to the iPad. Unfortunately, iOS devices do not support USB or Bluetooth from devices not approved by Apple. Today, dAISy either requires a Raspberry Pi (running Kplex or similar) or some tinkering with an ESP8266. Once it has native NMEA output, dAISy will also work with NMEA routers, some of which include WiFi.

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Now with DC/DC converter and lab tested:


I have a few spares and still look for volunteers for real-world testing.


The DC/DC converter didn't noticeably increase  the noise floor, so I think it should be fine. It is a ROF-78E5.0-0.5SMD-R from Recom Power. 9-36V input, 5V output at up to 500mA, and there's also a 3.3V version. Available for about $3.30 in singles at Digi-Key and Mouser.


Next: Reducing BOM cost, those connectors are pretty big and cost as much as the DC/DC converter. Does anyone know if terminal blocks are standardized, i.e. whether you can match and mix plug and jack? For some reason Phoenix Contact has really crappy drawings in their datasheets.

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