EF_I2S

General Information

• Maturity: Integrated
• Certification: EF Certified
• Provider: Efabless
• License: Apache Open Source
• Category: Logic
• PDK: SOFT IP

Overview

Two-wire I2S synchronous serial interface, compatible with I2S specification.

• Receiver only
• 32x32 Receive FIFO
• Sample Size selection
• Left channel, Right channel only or Stereo
• Programmable prescaler
• Supports both the classical I2S and the Left-aligned formats
• Programmable sample size
• Zero/Sign extension for the samples

The wrapped IP

APB, AHBL, and Wishbone wrappers, generated by the BusWrap bus_wrap.py utility, are provided. All wrappers provide the same programmer's interface as outlined in the following sections.

Wrapped IP System Integration

Based on your use case, use one of the provided wrappers or create a wrapper for your system bus type. For an example of how to integrate the APB wrapper:

EF_I2S_APB INST (
       `TB_APB_SLAVE_CONN,
       .ws(ws),
       .sck(sck),
       .sdi(sdi)
);

NOTE: `TB_APB_SLAVE_CONN is a convenient macro provided by BusWrap.

Implementation example

The following table is the result for implementing the EF_I2S IP with different wrappers using Sky130 PDK and OpenLane2 flow.

The Programmer's Interface

Registers

RXDATA Register [Offset: 0x0, mode: r]

The received sample

PR Register [Offset: 0x4, mode: w]

The Prescaler register; used to determine the sck signal frequency . $Prescaler = clk_freq/(2 x sck_freq) - 1$.

AVGT Register [Offset: 0x8, mode: w]

The Average threshold

CTRL Register [Offset: 0xc, mode: w]

Control Register; 0:Enable, 1:FIFO Enable.

CFG Register [Offset: 0x10, mode: w]

Configuration Register, 0-1: Channels to read, '01': right, '10': left, '11': Both (stereo) 2: Sign Extend 3: Left Justify 4-8: Sample Size (0-31)

RX_FIFO_LEVEL Register [Offset: 0xfe00, mode: r]

RX_FIFO Level Register

RX_FIFO_THRESHOLD Register [Offset: 0xfe04, mode: w]

RX_FIFO Level Threshold Register

RX_FIFO_FLUSH Register [Offset: 0xfe08, mode: w]

RX_FIFO Flush Register

Interrupt Flags

The wrapped IP provides four registers to deal with interrupts: IM, RIS, MIS and IC. These registers exist for all wrapper types generated by the BusWrap bus_wrap.py utility.

Each register has a group of bits for the interrupt sources/flags.

• IM: is used to enable/disable interrupt sources.

• RIS: has the current interrupt status (interrupt flags) whether they are enabled or disabled.

• MIS: is the result of masking (ANDing) RIS by IM.

• IC: is used to clear an interrupt flag.

The following are the bit definitions for the interrupt registers:

The Interface

Module Parameters

Ports

F/W Usage Guidelines:

1. Set the prescaler value in the PR register where sck_freq = (clk_freq / (prescaler+1))/2. Note that for the controller to function correctly, the prescaler needs to be greater than 1.
2. Check the I2S device data sheet to know the sample size sent and configure the sample_size field in the CFG reg accordingly.
3. Check the I2S device data sheet to know if the samples sent are in left justified or i2s mode and configure the left_justified field in the CFG reg.
4. Configure the channels field in CFG by specifying which channel you want to capture or both channels (stereo)
5. If you want the sample to be sign extended by the controller, enable sign_extended field in CFG register
6. After configuring the controller, enable it along with the FIFO to capture the samples by setting en and fifo_en fields in the CTRL register.
7. If you want to use the averaging feature in the controller, you can set the avg_en field and set the average threshold AVGT register. The average flag AVGF will be fired when the average of the samples sent are above this threshold. Note that the averaging mode works only when the sign extension mode is on.

Installation:

You can either clone repo or use IPM which is an open-source IPs Package Manager

• To clone repo: git clone https://github.com/efabless/EF_I2S
• To download via IPM , follow installation guides here then run ipm install EF_I2S

Run cocotb UVM Testbench:

In IP directory run:

cd verify/uvm-python/

To run testbench for design with APB

To run all tests:

make run_all_tests BUS_TYPE=APB

To run a certain test:

make run_<test_name> BUS_TYPE=APB

To run all tests with a tag:

make run_all_tests TAG=<new_tag> BUS_TYPE=APB

To run testbench for design with APB

To run all tests:

make run_all_tests BUS_TYPE=AHB

To run a certain test:

make run_<test_name> BUS_TYPE=AHB

To run all tests with a tag:

make run_all_tests TAG=<new_tag> BUS_TYPE=AHB

For more information see the repo on GitHub.