Finding duplicate messages in pipe

Ward

Hey so I'm using pipe to send messages from the render function to an auxiliaryTask which then sends it over USB serial. On the other end of the USB is an ESP32 driving a SPI display and some other stuff. I've ran into the issue that sometimes the ESP32 is overloaded and crashes or messes up data. Ofc this only happens when I'm sending a lot of data.

dataflow:
render --> pipe --> auxtask --> USB serial --> ESP32 --> SPI --> display

The solution I thought of was looking for duplicates in the pipe. Then I would only send the most recent command from all commands stored in the pipe with the same command type to reduce data. The data I'm sending from the Bela to the ESP32 is an int as command type and then two ints of data.

Inside the pipe data is stored as struct with an enum (data type), an int (value 1) and another int (value 2).

giuliomoro

you cannot observe the content of the Pipe, but you can extract all of it ("drain"). What I'd do if only the most recent value is what matters is:

struct PipeData data;
bool newData = false;
while(pipe.readNonRt(data))
{
  // set a flag that we received something, but don't do anything with the data yet
  newData = true;
}
if(newData)
{
  // now `data` contains the latest data.
  // send `data` to the display
}

Clearly, it would be cheaper if you could avoid sending to the pipe stuff that is going to be overwritten, but I guess the above should be an efficient-enough workaround.

Ward

That would work though the pipe contains different message types (as specified by the enum) and from each type I would only want the last one. I'm probably going to empty the pipe in an array and look for the most recent one of each message type.

I saw that you forked olikraus/u8g2 on github. Am I correct in assuming you're looking into the feasibility of porting that library to Bela? If so, and if SPI displays (SSD1322 in my case) would be supported, that would eliminate the ESP32 altogether and with that probably also my issue.

giuliomoro

Ward from each type I would only want the last one.

You could have one separate pipe for each type of message, or do what you suggested.

Ward saw that you forked olikraus/u8g2 on github. Am I correct in assuming you're looking into the feasibility of porting that library to Bela?

I turned it into a stand-alone OSC-OLED bridge here https://github.com/giuliomoro/O2O .
Only I2c displays are supported at the moment, but it shouldn't be too complicated to add SPI support. I think it would be a matter of having a couple of files like these linux-i2c ones https://github.com/giuliomoro/O2O/tree/main/u8g2/common which implement SPI instead. You could give it a try. Using the Bela SPI library it shouldn't be too complicated