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I am currently involved in designing a custom ESP32 board (ESP32-WROOM-32E) and adding the FT2232H chip for JTAG debugging to avoid having to get a FT2232H breakout board or ESP-PROG.

I have a question. What are EECS, EECLK, EEDATA pins for in the FT2232H chip and do I need it for JTAG or is it for another protocol? Ive read online that is for EEPROM which has something to do with temporary memory and programming.

edit: Not sure if I can just copy the schematics of an ESP-PROG or other FT2232H breakout boards since they use the FT2232H for other purposes like USB to UART (we are already using cp210x) and probably more.

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  • \$\begingroup\$ There are too many different ESP32s, do you have a specific part number ? \$\endgroup\$
    – Nipo
    Jan 10 at 15:28
  • \$\begingroup\$ ah sorry, I am using the ESP32-WROOM-32 @Nipo \$\endgroup\$
    – cr1tical1
    Jan 10 at 21:19
  • \$\begingroup\$ You've seen it's NRND, right ? \$\endgroup\$
    – Nipo
    Jan 10 at 21:26
  • \$\begingroup\$ sorry I meant ESP32-WROOM-32E..., I can see that it wants me to use IO14, IO12 ,IO13 and IO15 \$\endgroup\$
    – cr1tical1
    Jan 10 at 22:14
  • \$\begingroup\$ download the esp32-prog schematics and copy the connections \$\endgroup\$ Jan 11 at 0:17

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Fielded this exact question at work this week (although it was a programming interface for a PIC, not an ESP).

Yes, you need to attach an EEPROM to the FT2232H. While it's considered optional, in this scenario it's quite important to have. The reason is that the EEPROM defines the idle states for the signal and GPIO lines of your programming port. If you omit the EEPROM, you'll risk a situation where you can program and debug your board just fine when the debug USB connection is active, but as soon as you turn off the USB debugger, your chip goes into reset and doesn't work.

The EEPROM provides some nice additional capabilities as well, such as the ability to set string descriptors so you can distinguish this FTDI virtual serial port from others attached to the same USB host.

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  • \$\begingroup\$ Thank you, i will add the stuff for eeprom. Apart from power, oscillation, reset, ref and the first 4 pins (AD0-AD3) are there any other pins needed for jtag? \$\endgroup\$
    – cr1tical1
    Jan 12 at 7:08

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