Bigi LED display: Skillnad mellan sidversioner

# '''Idle:''' Clk is low. Data 1/2 are "don't care". During this period the display is off.

# '''Data transfer:''' 2 packets of 64 bits are transferred on each of the data lines, to the shift registers. Each new bit is shifted in from the data lines on the rising edge of clk. The display is kept off during this period by the control circuitry on the panel boards. If it wasn't, a lot of random image data would be shown on the display as it's shifted out to its final destination. The meaning of the bits is described below. The stock controller has a 200 ns low/300 ns high timing for clk, but this should be pretty lax as long as you don't leave clk high for long enough to strobe the LEDs, or run it too fast for the 74LS logic on the board.

# '''Strobe:''' After the last pulse data transfer is performed, clk is left at high signal level, which enables display output after a few microseconds. This lights up one line segment of the display with the data that was just transmitted. The length of the strobe time is controlled by the external device, but the stock controller is using a 720 µs strobe time.

# '''Idle:''' After the strobe, clk is pulled low which blanks the display. The stock controller leaves it low for 6.5 µs but it was measured that the line segment was typically turned off after 2 µs. Because 74x164 is clocked on rising edges but not falling edges, this does not produce a glitch during this period. This is also the next idle period, (1).

* First, 60 bits of each packet are color data, 0 for off and 1 for on. The value for the red subpixels are transferred on data 1, and the value for each green subpixel is transferred on data 2.

* Then, a bit indicating which group of the display should be activated is transferred. If the line belongs to the top half of the display, send 1 on data 1, otherwise send 1 on data 2. You could send 1 on both data lines, which will activate both the upper and lower half and mirror the image along the center line, but this is of course mostly useless.  

* Then a 3 bit line address is sent, which determines which line should be displayed.

* Since two panel identical boards are connected in series in this display, repeat he same sequence a second time with the display data for the other half.

* All data has now been transferred. Leave clk high for 720 µs (recommended) to strobe the line.

* Set clk low to blank the display. Leave clk low for at least 6 µs (recommended) before sending any more clock pulses to make sure the display is propely turned off.

== Image gallery ==

Bigi makerspace lights on.jpg|The Bigi display with lights in the room on.

Bigi makerspace lights off.jpg|The Bigi display with lights in the room off. Much better.

Bigi psu.JPG|The 10 kg absolute unit of a power supply unit.

Bigi connectors.JPG|The interface connectors and switches on the back of the display. All of these are unused due to the Arduino mod.

Bigi stickers.JPG|Original stickers showing the model number (MM2-2020 version 8806B) and serial number (724130).

Bigi closeup.JPG|Closeup of the Bigi logo