RA8875 Parallel VGA Card - Revision history

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Nuclear at 15:22, 31 August 2024

2024-08-31T15:22:42Z

Nuclear at 21:05, 28 August 2024

2024-08-28T21:05:06Z

Nuclear: Fill in specifications section

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2024-08-28T20:10:15Z

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@@ Line 22: / Line 22: @@
 == External Connection ==
-[[File:RA8875_VGA_Card_Pinouts.png|thumb|Board pinout|800px]]
+[[File:RA8875_VGA_Card_Pinouts.png|thumb|Board pinout|600px]]
-[[File:Expansion_port_pinout_on_RA8875_card_(any_variant).png|thumb|Expansion port pinout|800px]]
+[[File:Expansion_port_pinout_on_RA8875_card_(any_variant).png|thumb|Expansion port pinout|600px]]
-[[File:Teensy4.1_computer_external_headers_1.png|thumb|Teensy 4.1 Computer connector schematics, excluding the card connector, for comparison|800px]]
+[[File:Teensy4.1_computer_external_headers_1.png|thumb|Teensy 4.1 Computer connector schematics, excluding the card connector, for comparison|400px]]
 If you are on the Teensy 4.1 Computer board or any 5v microcontroller, you probably want to use the card connector.  Otherwise, I recommend soldering your connections to the large side expansion port.  You can read more on each in the sections below.

@@ Line 1: / Line 1: @@
 The RA8875 Parallel VGA Card is a small card which provides 800x480 pixel VGA output, using an 8-bit, 5v-compatible 8080-style data bus.  It uses the RA8875, which comes with many useful features for drawing, and includes built-in fonts, hardware scrolling, multiple layers, etc.
 == Detailed Specifications ==
@@ Line 21: / Line 23: @@
 [[File:RA8875_VGA_Card_Pinouts.png|thumb|Board pinout|800px]]
 [[File:Expansion_port_pinout_on_RA8875_card_(any_variant).png|thumb|Expansion port pinout|800px]]
@@ Line 44: / Line 44: @@
 This is a larger 3.3v-compatible port.

@@ Line 19: / Line 19: @@
 == External Connection ==
 If you are on the Teensy 4.1 Computer board or any 5v microcontroller, you probably want to use the card connector.  Otherwise, I recommend soldering your connections to the large side expansion port.  You can read more on each in the sections below.
@@ Line 29: / Line 36: @@
 === Card Connector ===
 This connector has all the needed lines to communicate with the RA8875, as well as level-shifting logic to make it completely 5v-compatible.  A pinout is provided above.
@@ Line 37: / Line 42: @@
 === Side expansion port ===
 This is a larger 3.3v-compatible port.

← Older revision		Revision as of 17:22, 3 September 2024
Line 17:		Line 17:

	This board is designed to work with the [[Teensy_4.1_Computer]], and is a convenient way of adding video output to the Teensy computer.		This board is designed to work with the [[Teensy_4.1_Computer]], and is a convenient way of adding video output to the Teensy computer.
		+
		+	== External Connection ==
		+
		+	If you are on the Teensy 4.1 Computer board or any 5v microcontroller, you probably want to use the card connector. Otherwise, I recommend soldering your connections to the large side expansion port. You can read more on each in the sections below.
		+	The rest of this section will be devoted to more nitty-gritty technical details.
		+
		+	There are two main connectors for interfacing to the RA8875, both share most of their pins and both are compatible with a respective connector on the [[Teensy 4.1 computer]].
		+	The card connector is a simpler, smaller header with pre-soldered headers, while the larger expansion port comes unsoldered and has more pins.
		+
		+	Both ports share the parallel pins WR, RD, and WAIT, as well as the busses ADDR and DATA. WR, RD, and WAIT are all active low, and it is expected that all select lines also be active low. The address bus (ADDR, shown on the board as A0, A1, and A2) has three pins, allowing for three addresses per device, but the RA8875 only uses addresses 0 and 1.
		+
		+	=== Card Connector ===
		+
		+	[[File:Card_Connector_Pinout.png\|thumb\|Card connector pinout\|800px]]
		+
		+	This connector has all the needed lines to communicate with the RA8875, as well as level-shifting logic to make it completely 5v-compatible. A pinout is provided above.
		+
		+	The card connector was originally designed to interface with cards for the Z80 computer I previously built, and has a compatible pinout, as well as a compatible electrical specification.
		+
		+	=== Side expansion port ===
		+
		+	[[File:Expansion_port_pinout_on_RA8875_card_(any_variant).png\|thumb\|Expansion port pinout\|800px]]
		+	[[File:Teensy4.1_computer_external_headers_1.png\|thumb\|Teensy 4.1 Computer connector schematics, excluding the card connector, for comparison\|800px]]
		+
		+	This is a larger 3.3v-compatible port.

← Older revision		Revision as of 15:22, 31 August 2024
Line 17:		Line 17:

	This board is designed to work with the [[Teensy_4.1_Computer]], and is a convenient way of adding video output to the Teensy computer.		This board is designed to work with the [[Teensy_4.1_Computer]], and is a convenient way of adding video output to the Teensy computer.
−
−	== Overall Design ==
−
−	[[File:Teensy41_Computer_Audio_circuit.png\|thumb\|Teensy 4.1 Computer audio circuit\|600px]]

@@ Line 10: / Line 10: @@
 ** Recommended settings use a 40Mhz pixel clock
 * 8-bit parallel data bus for fast writing
-** Overclocked up to 167.9Mbps with stable writing in tests
+** Overclocked to over 167.9Mbps with stable writing in tests
 ** Minimum cycle time of 55ns (see RA8875 datasheet)
 ** 5v compatible
 ** 8080-style control signals: nWAIT, nWR, nRD, nSEL
 ** Z80 and 8080 compatible design
 == Overall Design ==

← Older revision		Revision as of 20:24, 28 August 2024
Line 1:		Line 1:
		+	The RA8875 Parallel VGA Card is a small card which provides 800x480 pixel VGA output, using an 8-bit, 5v-compatible 8080-style data bus. It uses the RA8875, which comes with many useful features for drawing, and includes built-in fonts, hardware scrolling, multiple layers, etc.
−	Est li na svete,
		+
−	tsveti chto nye ?
		+	== Detailed Specifications ==
		+
		+	* Up to 480x800 pixel display
		+	* 16-bit color (RGB565)
		+	** Optionally, 8-bit color can be selected to use two drawing layers, and to improve bitmap draw time
		+	* Video modes can be selected or designed
		+	** RA8875 allows configuring of all VGA regions, as well as hsync and vsync polarity. Multiple resolutions and pixel clocks may be selected
		+	** Recommended settings use a 40Mhz pixel clock
		+	* 8-bit parallel data bus for fast writing
		+	** Overclocked up to 167.9Mbps with stable writing in tests
		+	** Minimum cycle time of 55ns (see RA8875 datasheet)
		+	** 5v compatible
		+	** 8080-style control signals: nWAIT, nWR, nRD, nSEL
		+	** Z80 and 8080 compatible design
		+
		+	== Overall Design ==
		+
		+	[[File:Teensy41_Computer_Audio_circuit.png\|thumb\|Teensy 4.1 Computer audio circuit\|600px]]