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OpenOCD and FTDI Chips

To let OpenOCD correctly drive the FTDI chip, we need to tell OpenOCD the hardware configuration of the FTDI chip through the config file:

### FTDI interface configuration ###
ftdi_vid_pid                0x0403 0x6010
ftdi_channel                0
ftdi_layout_init            0x0888 0x8B8B

Reference: https://openocd.org/doc/html/Debug-Adapter-Configuration.htmlarrow-up-right

We will analyze the config file line by line

ftdi_vid_pid                0x0403 0x6010

This line tells OpenOCD to find the USB device with the signature of corresponding vendor ID (VID) and product ID (PID).

0x0403: Future Technology Devices International Limitedarrow-up-right

0x6010: FT2232C/D/H Dual UART/FIFO IC

Selects the channel of the FTDI device to use for MPSSE operations. Here we select channel A, which is the first channel (channel 0).

Defines the initial data and IO direction of the GPIOs. The mapping is as follows:

0x

bit [15..8]

bit [7..0]

ACBUS[7..0]

ADBUS[7..0]

As an simple example, to initialize the JTAG LED on FT-LINK, which is an open-drain LED connected to ACBUS3 pin, we use the following setting

We can also define the JTAG_LED variable with the following command

Then, in the init routine, we can use the variable to reference this pin and blink the LED

note that since we are only enabling the output driver by the -oe flag, the chip can only drive it open-drain, and therefore we are only allow to set the signal state to either low (0) or high-Z (z).

If we try to set it to high (1), we will get the following error:

If we have some normal signal that we want to drive both high and low, we can use the -data flag instead:

If we somehow want all the states, we do the following

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