ADS8686SEVM-PDK: SPI Communication with FT232H (Pyftdi)

Tool/software:

Dear TI Support Team,

I am currently working on integrating the ADS8686S ADC with a FTDI FT232H USB-to-SPI bridge and encountering issues while trying to read the Device ID (Register 0x10) via SPI in software mode. Despite verifying signal activity through an oscilloscope, I am receiving incorrect or inconsistent values (e.g., 0x0002, 0xFFFF, 0x0000) instead of the expected Device ID.

Hardware Setup

ADS8686S Supply:

5.5V → T1 PWR 5.5

3.3V → T1 PWR DVDD

FT232H I/O Voltage: 3.3V

Shared GND between ADS8686S, FT232H, and power supply

Pin Connections

Note: R23 resistor on the ADS8686S board has been removed to allow SPI access.



Monitoring

  

Software For Test

from pyftdi.spi import SpiController

import time

def read_device_id():

spi = SpiController()

try:

spi.configure('ftdi://ftdi:232h:1/1')

port = spi.get_port(cs=0, freq=1000000, mode=0)

while True:

print("\n Reading DEVICE_ID (Register 0x10)...")

port.write([0x20, 0x00])

time.sleep(0.01)

response = port.exchange([0x00, 0x00], 2)

if len(response) == 2:

value = (response[0] << 8) | response[1]

print(f" Device ID: 0x{value:04X} ({value})")

else:

print(" No response received.")

time.sleep(1)

finally:

spi.terminate()

if __name__ == "__main__":

read_device_id()

SPI mode tested: 0 and 2

• Mode 2 (CPOL=1, CPHA=0) returns 0x0002.

• Mode 0 returns 0x0000.

• Oscilloscope Output: Confirmed proper SCLK and CS timing; data is transmitted as expected from FT232H.

Questions / Support Needed

1. Could the inconsistent Device ID values indicate a misconfiguration or hardware timing issue?

2. Is SPI mode 0 confirmed to be the correct configuration for the ADS8686S?

3. Is any additional configuration or initialization required on ADS8686S after reset to enable SPI register access?

4. Is there a way to verify that ADS8686S has entered software mode correctly (besides HWRNGSEL[1:0] = 00)?

5. Are there any known compatibility notes when using FT232H with ADS8686S?