04-06-2020, 08:00 PM
Just a bit of an update on this project.
I have been doing some work on the PCB. I like to work on all aspects of a project like this at the same time as a small component change can make the software easier/better or a change to the software can make the PCB layout easier etc.
I was hoping that I would be able to fit this project onto the same size PCB as Hedghog II and into the same case.
I started off with the Hedghog II PCB and removed the toggle and DIL switches as they will not be needed. I changed the location of the R2R DAC and juggled around the connections to some pins on the FPGA. With all this done there will be enough room for the frame store, microcontroller, 2 rotary encoders and a display.
The biggest obstacle to fitting it into the same case was the display. The display that I was using was a common 16 X 2 LCD display and it simply would not fit.
I decided to try a 128 X 32 pixel OLED display. They are tiny compared to the LCD display that I was using and would fit in the case. I thought the text on them may be too small to read. But to my surprise even when displaying 4 lines of text they are still easy enough to read. They come with two types of communication SPI or I2c. SPI is the fastest but the I2c type is easier to fit on the PCB. I use software I2c for programming the modulator chips because it is easy in software to create a SDA line for each modulator chip. Software I2c I found was too slow for the OLED display. It took too long to refresh. So I have it running from hardware I2c which gives acceptable results.
I have decided to stick with the AL422 frame store. I have made a lot of changes to the PCB and I felt changing the framestore as well might just be too much at once.
Picture of the OLED display with the 16 X 2 LCD alongside for comparison.
Frank
I have been doing some work on the PCB. I like to work on all aspects of a project like this at the same time as a small component change can make the software easier/better or a change to the software can make the PCB layout easier etc.
I was hoping that I would be able to fit this project onto the same size PCB as Hedghog II and into the same case.
I started off with the Hedghog II PCB and removed the toggle and DIL switches as they will not be needed. I changed the location of the R2R DAC and juggled around the connections to some pins on the FPGA. With all this done there will be enough room for the frame store, microcontroller, 2 rotary encoders and a display.
The biggest obstacle to fitting it into the same case was the display. The display that I was using was a common 16 X 2 LCD display and it simply would not fit.
I decided to try a 128 X 32 pixel OLED display. They are tiny compared to the LCD display that I was using and would fit in the case. I thought the text on them may be too small to read. But to my surprise even when displaying 4 lines of text they are still easy enough to read. They come with two types of communication SPI or I2c. SPI is the fastest but the I2c type is easier to fit on the PCB. I use software I2c for programming the modulator chips because it is easy in software to create a SDA line for each modulator chip. Software I2c I found was too slow for the OLED display. It took too long to refresh. So I have it running from hardware I2c which gives acceptable results.
I have decided to stick with the AL422 frame store. I have made a lot of changes to the PCB and I felt changing the framestore as well might just be too much at once.
Picture of the OLED display with the 16 X 2 LCD alongside for comparison.
Frank
