Versions Compared

Version Old Version 2 New Version Current
Changes made by

Catherine Spain

Sam Stuart

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

  1. Do not make the block sizes of your TDM ports too large. There is a limited amount of DMA memory on the Snapdragon and you may exceed this. (Audio Weaver testing has been with block sizes up to 5.0 msec.)

  2. You are only allowed to define a single TDM port as being the Synchronous Master. If you define multiple ports as Synchronous Master, then you will get a build error.

  3. You are allowed to place the TDM Port modules into different threads. For example, one port operates at a block size of 1 msec and is placed in thread 1A. A second port operates at a block size of 5 msec and is placed in thread 5A. A third port operates at a block size of 1 msec and is placed in thread 1B.

  4. Large block sizes lead to more efficient operation. You should restrict the small block sizes (0.25 and 0.5 msec) for use cases that require low latency. Other ports doing non-latency sensitive operations (like radio or Bluetooth), should use larger block sizes.

  5. If you stop a port, it will stop the audio DMA and interrupts. The DMA memory is freed up. When you start the port, DMA memory is reallocated and DMA interrupts start again. SA ports will restart and be time aligned to the SM port. SU ports will restart and resynchronize themselves to the SM port.

  6. The SM, SA, and SU ports have a single block size argument. This block size is used to set the block size of the DMA interrupt and also the block size at the output (or input) audio pins in Audio Weaver.

  7. The AS port has separate sample rates and block sizes for the device configuration and the Audio Weaver configuration. After stopping an AS device, you can change the device block size and sample rate, and these new values will be used when the port is restarted. This feature is specifically for interfacing with Bluetooth devices.

  8. TDM ports can only be accessed from the Hexagon DSPs. They are not available on the Arm.

  9. On the SA8255, the DSPs are all part of the early audio boot sequence and thus all TDM ports must be initialized during early audio. On NordySA8797/SA8397, only DSP0 is part of the early boot sequence. TDM ports can be on DSP0 and on DSP1 or DSP2 which are part of the late boot sequence.

...