RVMP (RTCM-VIA-MQTT-PROTOCOL) V0.2 (first very basic approach, but some features for future are in preperation). (GNU GPL V3)

In use by RVMT (RTCM Via MQTT Transmitter - https://github.com/hagre/RVMT_RTCM-VIA-MQTT-TRANSMITTER) using the MQTT msg/protocol (as a secure and opensource alternative to NTRIP) to get RTK correction data from BaseStations to Broker and to Rover GPS units.

Caster is on https://github.com/hagre/RVMT_RTCM-VIA-MQTT-CASTER

Basicly, this is a try to implement something like a NTRIP caster with MQTT features. There are a lot of similarities to NTRIP (V1.0/V2.0), because it is a known and usefull protocol with most needed features for this task.

Attension: Topics are casesensitive!!

• Basestation(s) are checking if a caster exists/is implemented or a simple base-client relay configuration is used

• Basestation(s) is/are publishing to MQTT broker (RTK/Base/...) and/or (RTK/MNTP/... - simple relay config) and deliver basic information (needed for Mountpointlist and ..)

• Basestationen are continuosly evaluating the RTCM input and presenting the avaliable feature (incl update if somthing new,..)

• Basestationen have to present relevant MNTPList msg if in use as simple relay

• Caster (if implemented) publish basic infos on RTK/Caster/... , to be recogniced by other users

• Caster (if implemented) is subscribing to broker and receiving all msg from connected basestations.

• Only caters have permission to read RTK/Base/... input

• Caster is keeping track of avaliable basstations (all, old and active ones).

• Caster is creating an Mountpointlist of possible active stations and publishing it to the broker under RTK/MNTPList/...

• Caster can activate RTCM transmission of connected and active basstation if needed

• Caster are tranforming/copy all the necessary RTCM datar from the RTK/Base/... to the RTK/MNTP/... topic (readeable for all RTK users)

• If a basestation is lost the last will show "off", the caster will remove it from the active Mountpointlist

• Clients can connect to the broker (user/password protected) and post the user id, this will request the caster to resend the Mountpointlist

• Clients can select to subscribe to the required RTCM msg from the desired MNTP (mountpoint) or all of them. RTK/MNTP//RTCM/#

• If the Client is leaving, the lastwill "byebye" gets activated.

• Caster can switch off publishing of the Basestations publishing RTCM (maintaining in STBY) if the last client has closed the subscription.

Welcome msg: (transmitted when a new connection is established, or a feature is updated, .. )

• RTK/Base/(NAME of BASE)/Status/Tversion/ - e.g "2.2" - Version of transmitter firmware [QOS = 1, retain = true, last_will = null] [read acces only by caster app, read/write by Basestation ]
• RTK/Base/(NAME of BASE)/Status/Pversion/ - e.g "0.1" - Version of protocol [QOS = 1, retain = true, last_will = null] [read acces only by caster app, read/write by Basestation ]
• RTK/Base/(NAME of BASE)/Status/RTCM/(TYPE of MSG)/ - e.g "1", "0.5" or "30" - time in seconds between update (~frequenz) [QOS = 1, retain = true, last_will = null] [read acces only by caster app, read/write by Basestation ]
• RTK/Base/(NAME of BASE)/Status/Operation/ - "ON" full working RTCM, "STBY" receiving RTCM, but not transmitting over MQTT, "ERROR" having some trouble, "OFF" - not avaliable [QOS = 1, retain = true, last_will = "OFF"] [read acces only by caster app, read/write by Basestation ]
• RTK/Base/(NAME of BASE)/Status/Error/ - type of error e.g "NO_RTCM_INPUT" [QOS = 1, retain = false, last_will = null] [read acces only by caster app, read/write by Basestation ] //further work required
• //planning to implement: RTK/Base/(NAME of BASE)/Status/Position/Lat/ - LatPosition [QOS = 1, retain = true, last_will = null] [read acces only by caster app, read/write by Basestation ] //further work required
• //planning to implement: RTK/Base/(NAME of BASE)/Status/Position/Long/ - LongPosition [QOS = 1, retain = true, last_will = null] [read acces only by caster app, read/write by Basestation ] //further work required
• //planning to try: RTK/MNTP/(NAME of BASE)/Command/Out/PW/ - e.g "Password" [QOS = 1, retain = false, last_will = null] [read acces only by caster app, read/write by Basestation ] //further work required
• //planning to try: RTK/MNTP/(NAME of BASE)/Command/Out/USER/ - e.g "Username" (? username == ) [QOS = 1, retain = false, last_will = null] [read acces only by caster app, read/write by Basestation ] //further work required

for each RTCM msg type:

• RTK/Base/NAME of BASE/RTCM// [retain = false, last_will = null] [read acces only by caster app, read/write by Basestation ]

• RTK/Base/(NAME of BASE)/Command/In/RTCM/
• RTK/Base/(NAME of BASE)/Command/In/GPS/
• RTK/Base/(NAME of BASE)/Command/In/Transmitter/
• //planning to try: RTK/Base/(NAME of BASE)Command/In/Serial/
• //planning to try: RTK/Base/(NAME of BASE)/Serial/In/

• RTK/Base/(NAME of BASE)/Status/Tversion/
• RTK/Base/(NAME of BASE)/Status/Pversion/
• RTK/Base/(NAME of BASE)/Status/RTCM/(TYPE of MSG)/
• RTK/Base/(NAME of BASE)/Status/Operation/
• RTK/Base/(NAME of BASE)/Status/Error/
• RTK/Base/(NAME of BASE)/Status/Position/Lat/
• RTK/Base/(NAME of BASE)/Status/Status/Position/Long/
• //planning to try: RTK/MNTP/(NAME of BASE)/Command/Out/PW/
• //planning to try: RTK/MNTP/(NAME of BASE)/Command/Out/USER/
• RTK/Base/(NAME of BASE)/RTCM/#

some calculation in the caster ....

• acvtivate or deactivate Basestations
• solve errors witch reboot if required
• copy RTCM from RTK/Base/(NAME of BASE)/... to RTK/MNTP/(NAME of MNTP)
• keep track of the Basestations
• construct and update Mountpointlist (all possible avaliable Basestations )
• keep track of the Basestations

• RTK/MNTP/(NAME of MNTP)/RTCM/(TYPE of MSG)/ [retain = false, last_will = null] [read acces by all RTK users, read/write by caster] commands to Basestation
• RTK/MNTP/(NAME of MNTP)/Command/In/RTCM/ - "ON" or "OFF" to activate/deactivate RTCM transmission if required [QOS = 1, retain = false, last_will = null] [read/write acces by caster app, read by correct Basestation ]
• RTK/MNTP/(NAME of MNTP)/Command/In/GPS/ - "REBOOT" to force an GPS reboot [retain = false, last_will = null] [QOS = 1, read/write acces by caster app, read by correct Basestation ]
• RTK/MNTP/(NAME of MNTP)/Command/In/Transmitter/ - "REBOOT" to force an transmitter reboot (e.g ESP32 modul) [QOS = 1, retain = false, last_will = null] [read/write acces by caster app, read by correct Basestation ]
• RTK/MNTPList/(NAME of BASE)/Status/Pversion/ [QOS = 1, retain = true, last_will = null] [read/write acces by caster app, read by clients ]
• RTK/MNTPList/(NAME of BASE)/Status/RTCM// [QOS = 1, retain = true, last_will = null] [read/write acces by caster app, read by clients ]
• RTK/MNTPList/(NAME of BASE)/Status/Operation/ [QOS = 1, retain = true, last_will = null] [read/write acces by caster app, read by clients ]
• RTK/MNTPList/(NAME of BASE)/Status/Position/Lat/ [QOS = 1, retain = true, last_will = null] [read/write acces by caster app, read by clients ]
• RTK/MNTPList/(NAME of BASE)/Status/Position/Long/ [QOS = 1, retain = true, last_will = null] [read/write acces by caster app, read by clients ]

• RTK/User/Subscribe/(NAME of USER)/ - "(NAME of MNTP)" to request MNTP transmission, caster will provide needet data if on the mountpointlist [QOS = 1, retain = false, last_will = "ByeBye"] [read/write acces by clients app, read by caster ]

initially and refresh if needed

• RTK/MNTPList/# - get complete list or
• RTK/MNTPList/(NAME of MNTP)/# - get single desired MNTP continously
• RTK/MNTP/(NAME of MNTP)/Status/Operation/ - check operation of desired MNTP
• RTK/MNTP/(NAME of MNTP)/RTCM/# - get all RTCM msg avaliable or
• RTK/MNTP/(NAME of MNTP)/RTCM/(TYPE of MSG)/ - just for each desired msg type

• //planning: RTK/Base/(NAME of BASE)/Serial/Out/

• //planning: RTK/Base/(NAME of BASE)/Serial/In/ - Serial transmission to GPS if required (config of chip) [retain = false, last_will = null] //serial transmission will be included in a later version
• //planning to try: RTK/Base/(NAME of BASE)/Command/In/Serial/ - "ON" or "OFF" to activate/deactivate Serial transmission to GPS if required (config of chip) [retain = false, last_will = null] //serial transmission will be included in a later version

• MNTP - Mountpoint
• (NAME of MNTP) == ""- e.g. XYZ01
• (TYPE of MSG) - e.g. 1074

+add PW acces for Basestation (if required at all) +add a special client ID (user "BaseMaintenance") for mantenance my basestations with serial com +serial com with base (RTK/Base/(NAME of BASE)/Command/In/Serial/ ...) in far future

• RTK/User/Subscribe/(NAME of USER)/Position/
• and construckt/calculate virtual basestation on user request for user position - give virtual name MNTP and publish accordingly