+- OpenMarine (https://forum.openmarine.net)
+-- Forum: OpenPlotter (https://forum.openmarine.net/forumdisplay.php?fid=1)
+--- Forum: General discussion (https://forum.openmarine.net/forumdisplay.php?fid=2)
+--- Thread: TTL level Onboard GPS PCB integration (/showthread.php?tid=5097)
TTL level Onboard GPS PCB integration - steved - 2024-01-14
Hello,
I am planning on making a portable OpenCPN/Autopilot system that I can easily move from one boat to the other. (One blue water cruiser no autopilot required and then a 'go-fast' fishing boat, need autopilot for kicker)
Both boats have different GPS connections (NMEA2000 and 0183) that leads to difficulty and not as much portability when moving the system from one boat to another.
GPS is rather important for tracks etc.
I am considering installing a older (I seem to have acquired a few of them) RGM-3550 'all in one' GPS receivers. The advantage of these are 3.3V operation as well as a -159dbm sensitivity. What this means is the GPS signal received inside the boat will be good, an external antenna is not required and the board could be mounted inside of the portable package.
The challenge for me arises with the interface. (I am very new to Raspberry development platforms and on a very steep learning curve) The RGM-3550 will output NMEA 0183 datastream at 9600n81 but at TTL level. This means that I would need to place a transceiver in between in order to use the standard UART interfaces.
What steps would I need to take to bit bash on GPIOs to receive the TTL data, or is there access to the TTL signal level that I can tie into after the Raspberry 4B transceiver?
A loose roadmap to the steps that I would need to take is appreciated. I am fine with the hardware implementation aspect and/or board modification. The big challenge is the implementation of this and integration of SignalK. -> As mentioned, I am on the steep part of the learning curve of this project.
Thank you in advance for suggestions on steps to proceed or ideally, this is not a new idea and there is a link somewhere with some additional documentation to assist.
Cheers,
Steve
RE: TTL level Onboard GPS PCB integration - PaddyB - 2024-01-15
As it is still serial data might be worth trying the output in a rs232 serial / usb adaptor. Pretty sure I've used serial data at ttl levels before fine is a cheal serial USB adaptor before.