[JASA 1C2] SoC Harness Functions User Logic Debug – Caravel SoC

Version: 2024/05/29

Table of Contents:

1. Introduction
2. Software Setup
3. Hardware Setup
4. Firmware
5. User Logic Debug Function
6. Caravel’s logic analyzer

1. Introduction

To evaluate the feasibility of realizing the JASA Chip 1 using eFabless design and manufacturing processes, we will assess the “user circuit debug function” using the “Marmot1” logic placed in the MPW-6 open project area. This evaluation involves creating a Caravel program and testing its functionality. By running “Marmot1” on MPW-6, we aim to demonstrate the design flow intended for use in JASA Chip 1.

2. Software Setup

Please follow the software setup in the previous investigation.

3. Hardware Setup

3.1 Pinouts

Caravel mprj_io[#]	Caravel Mgmt. SoC	Marmot IOF0	Marmot GPIO
0	JTAG	–	–
1	SDO	TDO	–
2	SDI	TDI	–
3	CSB	TMS	–
4	SCK	TCK	–
5	ser_rx	uart0_rx	–
6	ser_tx	uart0_tx	–
7	irq	spi1_csb[1]	gpio[24]
8	flash2_csb	spi0_flash_csb	–
9	flash2_sck	spi0_flash_sck	–
10	flash2_io[0]	spi0_flash_io[0]	–
11	flash2_io[1]	spi0_flash_io[1]	–
12	–	spi0_flash_io[2]	–
13	–	spi0_flash_io[3]	–
14	–	spi1_csb[0]	gpio[0]
15	–	spi1_sck	gpio[1]
16	–	spi1_io[0]	gpio[2]
17	–	spi1_io[1]	gpio[3]
18	–	spi1_io[2]	gpio[4]
19	–	spi1_io[3]	gpio[5]
20	–	spi2_csb	–
21	–	spi2_sck	–
22	–	spi2_io[0]	–
23	–	spi2_io[1]	–
24	–	spi2_io[2]	–
25	–	spi2_io[3]	–
26	–	i2c0_sda	gpio[12]
27	–	i2c0_scl	gpio[13]
28	–	i2c1_sda	gpio[14]
29	–	i2c1_scl	gpio[15]
30	–	uart1_rx	gpio[16]
31	–	uart1_tx	gpio[17]
32	–	uart2_rx	gpio[18]
33	–	uart2_tx	gpio[19]
34	–	uart3_rx	gpio[20]
35	–	uart3_tx	gpio[21]
36	–	uart4_rx	gpio[22]
37	–	uart4_tx	gpio[23]

3.2. Prepare the Caravel Board:

Ensure the Caravel board is powered off before starting the setup.
Ensure that the M.2 card with Marmot1 MPW-6 is properly inserted into the M.2 connector and securely fastened with a screw.。

3.3. Hardware Connection:

Connect an external SPI Flash module W25Q32 (flash2) to the Caravel board as below:

Caravel Board	Marmot IOF0	Flash2
3V3		VCC
GND		GND
mprj_io[8]	spi0_flash_csb	CS
mprj_io[9]	spi0_flash_sck	CLK
mprj_io[10]	spi0_flash_io[0]	DI
mprj_io[11]	spi0_flash_io[1]	DO

Connect an AHT20 sensor module to the Caravel board as below:

Caravel Board	Marmot IOF0	AHT20
3V3		VIN
GND		GND
mprj_io[26]	i2c0_sda	SDA
mprj_io[27]	i2c0_scl	SCL

And the USB to TTL module (3.3V) as below:。

Caravel Board	Marmot IOF0	USB to TTL
GND		GND
mprj_io[5]	uart0_rx	Tx
mprj_io[6]	uart0_tx	Rx

Our hardware setup is now complete and ready for testing.

4. Firmware

4.1. PicoRV32 Core

Run below commands to build the firmware and flash it to the Caravel Management SoC:

cd ~/caravel_samples/picorv32/marmot
make clean
make
sudo make flash

After flashing the firmware to the PicoRV32 Core, the LED D3 on Caravel board will start blinking.

4.2. Rocket Core

The firmware for the Rocket Core will be put in the external SPI flash memory “flash2” (W25Q32).

To flash the external SPI Flash (W25Q32), we will use the user passthru mode.
At first, we need to connect the CS pin of SPI Flash to mprj_io[3] instead of mprj_io[8].

Run below commands to build the firmware and flash it to the external SPI flash memory:

cd ~/caravel_samples/rocket/hello
make clean
make
sudo make flash2

After flashing the “flash2”, we need to reconnect the CS pin to mprj_io[8] so that the Rocket core can access and execute commands from the SPI Flash memory.

Press RESET button and we can see the Rocket Core output via UART (baudrate 115200).。

5. User Logic Debug Function

5.1. GPIO

Follow the steps below:

1. Connect the CS pin of “flash2” to mprj_io[3]
2. Run below commands to flash the firmware to the Rocket Core:

cd ~/caravel_samples/rocket/gpio
make clean
make
sudo make flash2

3. Connect the CS pin of “flash2” back to mprj_io[8]
4. Press RESET button

We could get the signal from gpio pins.
Please check the table Pinouts for the corresponding pin.
For example, gpio0 is mprj_io[14] on the Caravel board.

5.2. UART

Caravel mprj_io[#]	Caravel Mgmt. SoC	Marmot IOF0	Marmot GPIO
5	ser_rx	uart0_rx	–
6	ser_tx	uart0_tx	–
30	–	uart1_rx	gpio[16]
31	–	uart1_tx	gpio[17]
32	–	uart2_rx	gpio[18]
33	–	uart2_tx	gpio[19]
34	–	uart3_rx	gpio[20]
35	–	uart3_tx	gpio[21]
36	–	uart4_rx	gpio[22]
37	–	uart4_tx	gpio[23]

Follow the steps below:

1. Connect the CS pin of “flash2” to mprj_io[3]
2. Run below commands to flash the firmware to the Rocket Core:

cd ~/caravel_samples/rocket/uart
make clean
make
sudo make flash2

3. Connect the CS pin of “flash2” back to mprj_io[8]
4. Press RESET button

We could see the output from UART0:

And UART1 – UART4

5.3. I2C

Caravel mprj_io[#]	Marmot IOF0
26	i2c0_sda
27	i2c0_scl
28	i2c1_sda
29	i2c1_scl

Follow the steps below:

1. Connect the CS pin of “flash2” to mprj_io[3]
2. Run below commands to flash the firmware to the Rocket Core:

cd ~/caravel_samples/rocket/i2c
make clean
make
sudo make flash2

3. Connect the CS pin of “flash2” back to mprj_io[8]
4. Press RESET button

We can read the temperature and humidity from AHT20 sensor and output them to UART0.

5.4. SPI

Caravel mprj_io[#]	Marmot IOF0
14	spi1_csb[0]
15	spi1_sck
16	spi1_mosi
17	spi1_miso

Follow the steps below:

1. Connect the CS pin of “flash2” to mprj_io[3]
2. Run below commands to flash the firmware to the Rocket Core:

cd ~/caravel_samples/rocket/spi
make clean
make
sudo make flash2

3. Connect the CS pin of “flash2” back to mprj_io[8]
4. Press RESET button

6. Caravel’s logic analyzer

The logic analyzer is a 128-bit port going to/from the user area and management SoC. It allows the SoC to “probe” any desired signals from the user area after fabrication (but they cannot be changed once fabricated). This is useful for debugging signals during the bringup process, possibly to discover bugs in the hardware, or to verify that they are working correctly.

In the Marmot1 user logic, the lowest 32-bit port is connected to gpio0 – gpio31.。

To run LA test, follow the steps below:

1. Run below commands to flash the firmware to PicoRV32 Core:

cd ~/caravel_samples/picorv32/la
make clean
make
sudo make flash

2. Connect the CS pin of “flash2” to mprj_io[3]
3. Run below commands to flash the firmware to the Rocket Core:

cd ~/caravel_samples/rocket/gpio
make clean
make
sudo make flash2

4. Connect the CS pin of “flash2” back to mprj_io[8]
5. Press RESET button

We could get logs on UART0 from PicoRV32. The baud rate of PicoRV32 UART is 9600.