Reading SPI Flash Device IDs with the Aardvark Host Adapter

Reading the JEDEC Device ID from an SPI flash chip is the essential first step in any flash programming workflow. It confirms that the Aardvark I2C/SPI Host Adapter can communicate with the flash device, verifies the device manufacturer and part number, and validates the SPI bus configuration (clock polarity, phase, bit rate, and chip select) before attempting to program or read flash contents.

The JEDEC Read ID Command

The Read Identification command is defined by the JEDEC SFDP (Serial Flash Discoverable Parameters) standard and is supported by virtually all SPI NOR flash devices. The command sequence is:

1. Assert chip select (SS active low).
2. Send opcode 0x9F on MOSI.
3. Clock 3 additional bytes while reading MISO, these are the 3-byte Manufacturer and Device ID.
4. De-assert chip select.

For example, a Micron M25P32 responds with 20 20 16 (hex): manufacturer ID 0x20 (Micron/STMicroelectronics), memory type 0x20 (SPI NOR), and memory capacity 0x16 (32 Mbit). A Winbond W25Q32JV responds with EF 40 16: manufacturer 0xEF (Winbond), type 0x40, capacity 0x16 (32 Mbit).

Step-by-Step with Control Center

1. Connect the Hardware

Connect the Aardvark to the SPI flash target using a 10-pin ribbon cable. The pin mapping is:

Aardvark Pin	Signal	Flash Pin
1	SCK	CLK
3	MOSI	DI (Data In)
5	MISO	DO (Data Out)
7	SS	CS (Chip Select)
9	GND	GND
10	VCC (target power)	VCC

Enable Target Power in the Aardvark menu to supply 3.3V/5V to the flash device if it is not otherwise powered.

2. Configure SPI Settings

In Control Center Serial Software, set the SPI parameters:

• Polarity: Rising/Falling (SPI Mode 0 for most flash devices)
• Phase: Sample/Setup
• Bit Rate: 1 MHz (conservative starting point, increase after communication is verified)
• Bit Order: MSB first
• Slave Select: Active Low

3. Send the Read ID Command

In the SPI Master panel, enter the MOSI data: 9F 00 00 00

The first byte (0x9F) is the Read ID opcode. The three 0x00 bytes are dummy bytes that clock out the 3-byte device ID response on MISO. The Aardvark transmits on MOSI and simultaneously receives on MISO.

4. Read the Response

Control Center displays both the MOSI (transmitted) and MISO (received) data. The MISO bytes corresponding to the three dummy bytes contain the Device ID. The first MISO byte (corresponding to the opcode byte) should be ignored, it is undefined during the command phase.

Verification and Next Steps

If the Device ID matches the expected value for your flash chip, the SPI bus configuration is confirmed correct and you can proceed to flash programming operations (erase, program, verify) using either Control Center, Flash Center Software, or the Aardvark API.

If the response is all 0xFF or all 0x00, check: chip select polarity, SPI mode (try Mode 3 if Mode 0 fails), target power, and physical connections.

Alternative Approaches

The same Read ID operation can be performed through:

• Flash Center Software: automatically reads the device ID during target device selection, with a built-in database of thousands of flash devices.
• Aardvark API: programmatically in C, Python, or C# for automated test scripts that need to verify flash device identity before programming.
• Cheetah SPI Host Adapter or Promira Serial Platform: same command sequence, higher clock speeds available (40+ MHz and 80 MHz respectively).

GSAS Micro Systems provides the Aardvark alongside the I2C/SPI Activity Board and SPI Flash Demo Board for teams learning SPI flash programming workflows across India.