Alloy possible projects

lawrie 2020-10-22 08:31:58 UTC #1

I have been thinking about what projects I would like to do with an Alloy board.

It would be nice to have some sort of display attached to the Alloy, which could be VGA/HDMI, or could be an LCD/Oled screen.

For an LCD screen the 240x240 16-bit colour SPI st7789 displays are very nice, and very cheap.

You could attach such a display to the Alloy using a Pmod or a feather wing or a breadboard.

I wrote drivers for such displays on the Blackice, but the best one I know of is this.

It would be fairly straightforward to convert that to nmigen.

I was thinking of using it to select files on the ESP32 to be sent to the fpga, e.g. roms to be executed by a CPU.

For that you could connect it to the Alloy Serial Bus and send the directory listing of the ESP32 to it. You would need at least three buttons to select a file (up, down and select).

There are lots of other possibilities for an LCD display such as using feather wings sold by Adafruit such as this one, which comes with the necessary buttons.

Folknology 2020-10-22 13:12:32 UTC #2

This posses one of the questions I think about on the Alloy, the example you point to from Adafruit is a feather peripheral using pins connected to the ESP32 in Alloys case. You may prefer to have the display driven by the Ice40, so you could use a flying lead instead (This display is I2C based). If however it was just simple text and small enough it doesn't matter.

I think for larger and or faster displays Spi or parallel based would be better, driven directly from the Ice40 using and internal dual-ported sort of arrangement, data could then be driven in from the ESP32 via the ABC..

lawrie 2020-10-22 15:30:03 UTC #3

Yes, I looked into that display more and saw it was i2c. And I had forgotten that all those feather wing pins were connected to the ESP32.

For the application that I was talking about, i.e. selecting a file to send to the FPGA, having a display connected to the ESP32 may be easier to program, but for other applications, particularly LCDs with a parallel interfaces, we would want to connect it to the FPGA.

Another application that I am interested in is driving the OV7670 camera. I currently have that camera working on the Ulx3s and the gateware (currently in Verilog) reads the camera and sends the image to an SPI SSD1331 display and to an HDMI monitor. See - https://github.com/goran-mahovlic/fpga-odysseus/tree/master/projects/OV7670-HDMI-OLED. I plan to convert that to use an ST7789 SPI display. The code I am using was converted from code I had working on the Blackice II some time ago, with a VGA display.

That would work well on the Alloy board with an LCD connected to the FPGA.

However, I believe you have the OV7670 i2c pins connected to the ESP32, so the camera configuration that I currently have in gateware (Verilog) would need to be converted to python on the ESP32.

Folknology 2020-10-22 15:58:14 UTC #4

Oops sorry I read it wrong first time around, yes the I2C is connected to the ESP-S2, I think folks have done quite a bit of camera config with ESP cams, so I2C configs should already be found on the internet I guess.

BTW the reason for doing this was to save the more valuable (higher bandwidth) Ice40 pins for other usage..

lawrie 2020-10-22 16:05:05 UTC #5

Will these camera modules connect to the Alloy board - https://www.ebay.co.uk/itm/VGA-OV7670-CMOS-Camera-Module-0-3-Mega-Pixel-Lens-CMOS-640X480-TOP/222058090216

Folknology 2020-10-22 16:10:13 UTC #6

Probably although I don't see a specification on that item about pinout/dimensions etc..

lawrie 2020-10-22 17:56:04 UTC #7

If I wanted to drive an LCD display from the fpga, but not use the Pmod, what are the options? For a 7 or 8 pin SPI display, I could possibly use the iceio connector, but that does not seem to have Vcc and Gnd. Would I get enough power to drive Vcc from an fpga pin?

The Ulx3s has a 7-pin connector with Vcc and Gnd for mounting Oled/LCD SPI displays which works for a variety of them including the SSD1331 and the ST7789.

For an 8-bit parallel display, the iceio connector is again a possibility but I guess I really need a carrier board for the type of LCD display,

Folknology 2020-10-22 18:14:35 UTC #8

Depending on size the Display board could be a carrier underneath facing away with buttons perhaps?

BTW bottom is better than top with Alloy as it is less likely to impede the wifi signal.

lawrie 2020-10-23 16:42:42 UTC #9

I wrote the nmigen driver for the ST7789 240x240 16-bit color LCD display - https://github.com/lawrie/ulx3s-nmigen-examples/blob/master/st7789/st7789.py

lawrie 2020-10-24 16:58:10 UTC #10

And I now have a partly working OV7670 camera controller in nmigen, showing the picture on the LCD display. I have not yet finished the camera configuration.

github.com

lawrie/ulx3s-nmigen-examples/blob/master/ov7670/camtest.py

import argparse

from nmigen import *
from nmigen.build import *
from nmigen_boards.ulx3s import *

from  camread import *
from  st7789 import *

# The OLED pins are not defined in the ULX3S platform in nmigen_boards.
oled_resource = [
    Resource("oled_clk",  0, Pins("P4", dir="o"), Attrs(IO_TYPE="LVCMOS33", DRIVE="4", PULLMODE="UP")),
    Resource("oled_mosi", 0, Pins("P3", dir="o"), Attrs(IO_TYPE="LVCMOS33", DRIVE="4", PULLMODE="UP")),
    Resource("oled_dc",   0, Pins("P1", dir="o"), Attrs(IO_TYPE="LVCMOS33", DRIVE="4", PULLMODE="UP")),
    Resource("oled_resn", 0, Pins("P2", dir="o"), Attrs(IO_TYPE="LVCMOS33", DRIVE="4", PULLMODE="UP")),
    Resource("oled_csn",  0, Pins("N2", dir="o"), Attrs(IO_TYPE="LVCMOS33", DRIVE="4", PULLMODE="UP")),
]

ov7670_pmod = [
    Resource("ov7670", 0,

This file has been truncated. show original

The connectors will need to be changed for Alloy, and configuration will need to be done from the ESP32.

My example is currently using a frame buffer for the LCD display, but that will be harder with the single-ported ram on the up5k.

It might be possible to just use a line buffer, but that will take very careful synchronization of the input and output signals, and writing to the LCD display will need to keep uf with the speed of the VGA camera.

Folknology 2020-10-24 19:02:38 UTC #11

This is excellent @lawrie I wonder would it be worth putting a connector on the board for this sort of application?

For example something that can connect to this display maybe and FPC type?

lawrie 2020-10-24 21:01:42 UTC #12

That is the display I am using, but with the breadboard type connector. An FPC connector would be excellent.

I now have the camera configured on the Ulx3s board and am getting a sharp 16-bit color image but clipped and downscaled to 240x240. There is currently a slight bug as the image is wrapping round.

If the board is going to have a camera connector and be used for image processing, I think it needs some default way to display the images. And HDMI and VGA are currently not that easy.

Folknology 2020-10-25 21:50:02 UTC #13

This display seems to be avaialble in a 24pin FPC, this would enable us to drive in either serial or parallel, selectable by a couple of pins from uC possibly..

lawrie 2020-10-26 08:32:30 UTC #14

That would be good if it is available at a reasonable price and you have enough fpga pins for that.

Would the idea be to have this connector instead of the iceio one? If so, it becomes more like the Raspberry Pi with its csi and dsi connectors.

Not sure how you would arrange things, so you can fix both the camera and the display to the device, pointing in the same direction (for selfies) or possibly opposite directions (to work like a camera with an lcd viewer).

Folknology 2020-10-26 14:11:13 UTC #15

We should definitely talk about this on the stream Wednesday, I will have some CAD by then..