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iAcommsDriver provides our standard interface between MOOS and the WHOI uModem. It implements the GOBY uModem driver class and allows other MOOS applications to make use of the modem through several MOOS variables. It provides provides two main methods of interface. The unified interface should be used by new applications, at least for receiving acomms messages. The simple interface is primarily designed for a human to use with uPokeDB, but can provide adequate transmission functionality for some applications.
Simple Interface
Great for simple applications or human use.
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- Two way ranging
- Driver crashes if pLogger is not started first
- Acomms stats may be incorrect if, for example, one and a fraction of three available frames are used
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pAcommsSimulator
pAcommsSimulator is designed to run on the shoreside MOOS community and provide a simulation back-end for any number of connected iAcommsDriver's.
Simulator Configuration
| Code Block |
|---|
ProcessConfig = pAcommsSimulator
{
IterateMode = 0 // regular iterate and mail
AppTick = 20
sound_speed = 1450 // m/s
p_partial_loss = 0.1
p_complete_loss = 0.1
p_sync_loss = 0.1
p_loss_per_frame = 0.5
} |
The currently loss configuration is:
p_partial_loss - probability that some, but not all frames are lost. In the case of single-frame packets, partial losses cannot occur.
p_complete_loss - probability that all frames are lost, but the packet is still received. One way ranging will also still occur.
p_sync_loss - probability that a packet is not heard at all. The receiver will never enter the receiving state.
p_loss_per_frame - given that a partial loss occurs, the probability that any given frame within the packet is lost. If no frames are lost after this probability is applied, one frame is randomly selected to be lost. Similarly, if all frames are lost, one frame is randomly preserved.
Given this configuration, the probability of no loss is simply:
p_no_loss = 1 - (p_partial_loss + p_complete_loss + p_sync_loss)
Except in the case of single-frame packets where it is:
p_no_loss = 1 - (p_complete_loss + p_sync_loss)
Driver Configuration
iAcommsDriver communicates with pAcommsSimulator by establishing a connection to the same MOOSDB the simulator is running on. An example iAcommsDriver configuration for simulation:
| Code Block |
|---|
ProcessConfig = iAcommsDriver
{
IterateMode = 0 // regular iterate and mail
AppTick = 5
PortName = /dev/ttyUSB1
ID = 5
PSK_minipackets = false
enable_ranging = true
show_range_pulses = true
in_sim = true
sim_server = localhost
sim_port = 9000
} |
In this case, the shoreside MOOS community on which pAcommsSimulator is running is found at localhost, port 9000.
Features
Implemented:
- Approximate timing of transmission/reception length for different rates
- All standard rates and mini packets
- One way travel times
- All fields used by HoverAcomms library
Not implemented:
- Complete / accurate receive statistics
- LBL pings
- two way ranging
If you are using the HoverAcomms library to interact with iAcommsDriver, you should not encounter any issues using the simulator. However many fields, particularly in the receive statistics, are either not populated or populated with dummy (and potentially incorrect) values by the simulator.