elixir-circuits
Latency
Setup
- Version: latest (with PR fork)
- OS: OSX
- Platform: MacBook Pro
Expected Behavior
No significant latency
Actual Behavior
Latency up to a second with modems set to 20ms window to minimise buffering
Steps to Reproduce the Problem
I have a pair of radio modems at close to point blank range set to 57600 baud sending a short < 100 byte message. The modems have a firmware maximum window size config of 20ms which is the setting normally used to minimise latency. I minimised the number of other messages (they support sending hundreds of messages of similar size with no throughput issues), and the same software setup running over WiFi/UDP has no noticable delay. However when I use the modems with one of them via circuits UART I get a latency delay of about a second. I have set the uart connection to active.
I know there are lots of variables in play here, but I was wondering if there are any configuration settings you would use to minimise latency of short messages when using this library?
Thanks, Robin
My use of Circuits UART isn't performance critical and I know that Circuits.UART performance could be improved. However, I wasn't expecting issues on an MBP at 57600.
Just so I understand right, the firmware at the other end times out since it doesn't receive a message in 20 ms. At 57600 baud, a 100 byte message takes about 17 ms to send. If it's delayed by 3 ms, then it times out?
Hi Frank,
Sorry the window size just means that it sends what it has in it’s buffers every 20ms. I can see the timeout arguments in the C code and mention of polling but don’t understand what it’s doing, and wondered if perhaps there was a polling interval or other setting in there that could be tweaked.
Cheers Robin
Does the firmware work with any other software on your Mac? For example, does it work with Picocom? It's sounding like it's not a Circuits.UART issue, but a general issue that writing bytes to the serial port doesn't work well.
Is the C code that you're referring to posted anywhere?