HPI loading method for DSP

The Host Port Interface (HPI) is a method used to communicate between a DSP (Digital Signal Processor) and a host processor (such as a microcontroller or general-purpose processor) in many Texas Instruments (TI) DSPs. The HPI loading method is typically used for transferring code, data, and parameters to the DSP from the host processor, which is often part of the system's boot or initialization procedure.

HPI Loading Method Overview:
The HPI provides a mechanism to transfer data to and from the DSP memory (usually on-chip SRAM or external memory) over a parallel bus interface. The loading method typically involves the following steps:

1.HPI Initialization:

• The Host Processor (such as a microcontroller, ARM, or another processor) initializes the HPI interface to communicate with the DSP. This includes setting up the HPI control registers, enabling the correct clocking for HPI, and possibly configuring the GPIO pins (if they are shared with other peripherals).
• The DSP typically waits for the host processor to start the data transfer.

2.Loading Code/Data:

• The host processor loads the program or data to the DSP’s memory (usually on-chip SRAM or external memory) over the HPI.
• The host writes the data to memory locations in the DSP through HPI registers. The data can include DSP code (for execution), configuration parameters, or runtime data.
• The data is written to specific addresses in the DSP's data memory or program memory depending on the system design.

3.Execution Start:

• After the DSP memory has been loaded with the necessary code or data, the host processor typically triggers the DSP to start executing the code. This is done by writing a control value to the DSP’s control register, which can initiate the execution of the loaded program.
• The host can also monitor the DSP's execution status or provide further commands via HPI.

4.Synchronization:

The HPI interface often uses interrupt signals or polling to synchronize the host and DSP during the loading process. The host can use interrupts to signal when data has been successfully loaded, or it can periodically check the DSP’s status register.

Typical Steps for HPI Loading:

1.Set Up Host Communication:

• Initialize the HPI interface on the host processor.
• Configure the DSP to accept HPI communication (usually involves setting the DSP’s HPI control register and ensuring the DSP is in a waiting state).

2.Load Data/Code:

• Transfer the data from the host processor to the DSP memory. This can be done in chunks (e.g., 32-bit or 64-bit words).
• The host writes the data to memory locations in the DSP’s program memory or data memory.

3.Start Execution on the DSP:

• Once the DSP memory is loaded, the host processor signals the DSP to begin execution, often by writing to a control register.
• This could be as simple as setting a flag or sending a command to the DSP to begin fetching instructions from memory.

4.Error Checking/Verification:

The host may implement error checking mechanisms to ensure the data was correctly loaded and to handle any issues, such as verifying the checksum of the loaded data or checking for completion.

Example of the Process:

Let's consider a DSP system where we are loading a simple DSP program
into the memory via HPI:

1.Host Processor Setup (e.g., ARM or Microcontroller):

Set up HPI control registers.

• Initialize the GPIO pins for the HPI interface.
• Configure memory regions that will hold the data to be loaded (e.g., program or data memory).

2.Data Transfer:

• The host writes a small piece of the DSP program into memory (e.g., 32-bit data chunks).
• After each chunk is written, the host checks the DSP’s memory to ensure the correct data is in place (via polling or interrupt).

3.Execution Trigger:

After loading the entire program, the host writes a signal to the DSP’s control register to trigger the start of execution.

4.Completion and Monitoring:

The host may wait for the DSP to finish execution or periodically check its status via HPI, allowing synchronization of the two processors.

Tools and Libraries for HPI Loading:

• TI Code Composer Studio: For development on TI DSPs, Code Composer Studio provides a development environment that supports HPI communication. It can be used to load and debug code running on DSPs over HPI.
• Host Software: You would typically write software on the host processor to manage the HPI interface and facilitate the loading of data to the DSP. This could involve direct register manipulation or using a communication library.

Conclusion:
The HPI loading method allows for efficient communication between a host processor and a DSP for code and data loading. The process typically involves setting up the HPI interface, transferring data to the DSP's memory, triggering execution, and ensuring synchronization. This method is widely used in applications where the DSP needs to be programmed dynamically from a host system, such as in embedded systems, real-time signal processing, and communications systems.