Access ACBUS and use it as GPIO?

[eblot]

Access ACBUS and use it as GPIO?

I found some useful code as a work around in issue 38 by chadkennedyonline:
#38

but I'm still wondering is it possible to add acbus control in library?

[eblot]

Yes it should be possible using the SET_BITS_HIGH command. It has already been implemented with SPI mode.

Thanks a lot,I can configure the ACBUS using SpiController().get_gpio() now.

[eblot]

Re-opening this feature request as it would be great to provide GPIO support for ACBUS with bit bang mode as well.

[darlington72]

Dear all,

Finally, is it possible to control both SPI on AD0/1/2 and CS on AD4 + an extra gpio output on AC3 with an FT2232D?
In my case, the SPI perfectly works with AD0/1/2 and CS on AD4 but I can't add the extra gpio output on AC3.

Im in an Ubuntu environnement, with python3, pylibftdi 0.16.1.2, pyusb 1.0.0 and pyftdi 0.28.5.
I tried the example "Example: communication with a SPI device and an extra GPIO".

Thank you!

[eblot]

There was an issue with ACBUS, it should now be supported (v0.28.7), which has been tested with a FTDI2232H.

I do not have a FT2232D at hand - this is a really legacy device, I'm afraid I cannot test it by now.

[darlington72]

Dear Mr Blot,

Thanks for your answer and to added example on spi with gpio access.
I don't understand the philosophy on how to use functions. In my case, I'm working with:
AD0: SCLK, AD1: MOSI, AD2: MISO, AD4: /CS (AD3 unused)
+AC3 a gpio output.
I suppose I should:

1. self._spi.get_port(0, freq=1E6, mode=0)
2. self._spi.get_gpio()
3. self._io.set_direction(?,?)
4. self._io.write(?)
5. self._port.exchange(data,length)
6. self._io.write(0)

Is that the correct way to dessert the gpio pin, do an spi access (with CS on AD4) and then reassert the gpio pin? Which value should I put on the parameters?

I'll be able to confirm (or not) that the issue with ACBUS is supported on FT2232D.

Thank you!

[eblot]

/CS are supposed (at least with PyFtdi) be in-order, starting from the first pin after the three mandatory SPI signals (AD0/AD1/AD2). If you do not use AD3 for /CS, but you use AD4 for the first /CS signal, AD3 is still reserved for another /CS and cannot be re-used for GPIOs, i.e. in your case:

• AD0: SCLK
• AD1: MOSI
• AD2: MISO
• AD3: N.C.
• AD4: /CS
• AD5,AD6,AD7: GPIOs
• AC0,AC1,AC2,AC3: GPIOs

You still need to declare 2 /CS signal, and only use the second one, i.e.

 self._spi = SpiController(cs_count=2)  # AD3, AD4
 port = self._spi.get_port(1, freq=6E6, mode=3)  # port 0 is AD3, not used

then if you want to re-use the SPIO GPIO unit test, you need to perform the test on only 3 pins instead of 4, as there are only 3 AD pins available for GPIO, i.e. something roughly like this:

 ad_pins = ((1 << 3) - 1) << 5  # AD5-AD7 as input
 ac_pins = ((1 << 3) - 1) << 9  # AC1-AC3 as output
 io_pins = ad_pins | ac_pins

 # ...

 for ac_ in range(1 << 3):  # only 3 pins
    ac = ac_ << 1           # skip LSB (AD4/AC0)
    # ...

with:

• AD5 connected to AC1
• AD6 connected to AC2
• AD7 connected to AC3
• AC0 not connected

[darlington72]

I have an equipment (fpga) behind the ft2232D, so when I deassert and reassert AC gpios, I have something different than the example. But in my case, I confirm that your example with SPI + 2 extra GPIOS (/CS and ACBUS) perfectly works on the FT2232D.

Thank you!!

[eblot]

Ok, thanks for the feedback!