Teensy 4.1 Computer - Revision history

Nuclear: Fix mechanical measurements header size

2024-07-30T15:18:01Z

Fix mechanical measurements header size

Nuclear: Change size of mechanical measurements image

2024-07-29T14:05:26Z

Change size of mechanical measurements image

Nuclear: Change size of mechanical measurements image

2024-07-29T14:05:02Z

Change size of mechanical measurements image

Nuclear: Change size of mechanical measurements image

2024-07-29T14:04:18Z

Change size of mechanical measurements image

Nuclear at 14:03, 29 July 2024

2024-07-29T14:03:10Z

Nuclear: Add more images to the Expansion Ports section

2024-06-13T21:51:23Z

Add more images to the Expansion Ports section

Nuclear: Added information about the parallel port

2024-06-13T21:47:33Z

Added information about the parallel port

Nuclear: More expansion port docs

2024-06-13T21:40:45Z

More expansion port docs

Nuclear: Saving work on the expansion port documentation

2024-06-13T21:29:10Z

Saving work on the expansion port documentation

Nuclear at 20:51, 13 June 2024

2024-06-13T20:51:52Z

@@ Line 424: / Line 424: @@
 The card connector was designed to interface with cards for the Z80 computer I previously built, and has a compatible pinout.
-=== Mechanical Measurements ===
+== Mechanical Measurements ==
 [[File:Teensy4.1 desktop measurements.png|Board measurements|854px]]

← Older revision		Revision as of 14:05, 29 July 2024
Line 426:		Line 426:
	=== Mechanical Measurements ===		=== Mechanical Measurements ===

−	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|~~860px~~]]	+	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|854px]]

← Older revision		Revision as of 14:05, 29 July 2024
Line 426:		Line 426:
	=== Mechanical Measurements ===		=== Mechanical Measurements ===

−	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|~~900px~~]]	+	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|860px]]

← Older revision		Revision as of 14:04, 29 July 2024
Line 426:		Line 426:
	=== Mechanical Measurements ===		=== Mechanical Measurements ===

−	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|~~750px~~]]	+	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|900px]]

← Older revision		Revision as of 14:03, 29 July 2024
Line 423:		Line 423:

	The card connector was designed to interface with cards for the Z80 computer I previously built, and has a compatible pinout.		The card connector was designed to interface with cards for the Z80 computer I previously built, and has a compatible pinout.
		+
		+	=== Mechanical Measurements ===
		+
		+	[[File:Teensy4.1 desktop measurements.png\|Board measurements\|750px]]

@@ Line 345: / Line 345: @@
 [[File:Teensy4.1_computer_expansion_ports.png|thumb|Expansion port layout, not including the card connector port|800px]]
 There are three large expansion ports on the Teensy 4.1 computer board, and 5 smaller ports.  Here is a list, describing what each one breaks out:
@@ Line 414: / Line 415: @@
 === About the Parallel Port ===
 All three ports that provide parallel share the parallel pins WR, RD, and WAIT, as well as the busses ADDR and DATA.  Each connected parallel device should use a separate select pin, however, with pin 9 being reserved as the card connector's select pin.  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.  A parallel port is important to have because of the high bandwidth it provides.  The Teensy can write this port extremely fast, thus allowing better framerates and draw times for connected graphics devices.  I imagine there are other uses for this port as well.

← Older revision		Revision as of 21:47, 13 June 2024
Line 412:		Line 412:
	** The pinout is designed to be compatible with Sparkfun devices and serial pinouts		** The pinout is designed to be compatible with Sparkfun devices and serial pinouts
	** Provides 3.3v and ground		** Provides 3.3v and ground
		+
		+	=== About the Parallel Port ===
		+
		+	All three ports that provide parallel share the parallel pins WR, RD, and WAIT, as well as the busses ADDR and DATA. Each connected parallel device should use a separate select pin, however, with pin 9 being reserved as the card connector's select pin. 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. A parallel port is important to have because of the high bandwidth it provides. The Teensy can write this port extremely fast, thus allowing better framerates and draw times for connected graphics devices. I imagine there are other uses for this port as well.
		+
		+	As ADDR, WR, RD, and any select pins are all output-only from the Teensy, '''there is no level-shifting logic for them.''' For the WAIT line, there is a simple resistor voltage divider to take the 5v from the card connector down to 3.3v. There is only level-shifting logic provided for data lines on the card connector, so that 5v TTL devices and levels can be used with the card connector out of the box.
		+
		+	The card connector was designed to interface with cards for the Z80 computer I previously built, and has a compatible pinout.

@@ Line 344: / Line 344: @@
 == Expansion Ports ==
-[[File:Teensy4.1_computer_expansion_ports.png|caption|Expansion port layout, not including the card connector port|800px]]
+[[File:Teensy4.1_computer_expansion_ports.png|thumb|Expansion port layout, not including the card connector port|800px]]
 There are three large expansion ports on the Teensy 4.1 computer board, and 5 smaller ports.  Here is a list, describing what each one breaks out:
@@ Line 359: / Line 359: @@
 ** '''3.3v-compatible''' 8-bit parallel bus
 *** Particularly useful for LCD displays and LCD display controllers, or any other parallel peripheral, for very high speeds
-* Right-side expansion port (J10 - reference not shown on board revision 1.1)
+* Right-side expansion port (J12 - reference not shown on board revision 1.1)
 ** Designed for ATX-compatible expansions to the board
 ** Exposes 5v and 3.3v lines
@@ Line 368: / Line 368: @@
 *** Analog inputs: A4, A5
 * Card Expansion Port
-** Provides a '''5v-compatible''' 8-bit parallel port.  The pins are shared with the other parallel ports.  The port is '''not bidirectional'''
+** Provides a '''5v-compatible''' 8-bit parallel port.  The pins are shared with the other parallel ports.
 *** Controlled by write, read, and select lines.  Select pin is pin 9, pulling it low will enable communication.
 ** Provides only a 5v line.
-* I2S Expansion Port
+* I2S Expansion Port (J10)
 ** Provides an alternative to the 3.5mm audio output, and allows one to attach a microphone
 ** Breaks out I2S port 2
@@ Line 380: / Line 382: @@
 *** Analog pins A2 and A3
 *** UART4

← Older revision		Revision as of 21:29, 13 June 2024
Line 340:		Line 340:
	** 27.2uF ceramic		** 27.2uF ceramic
	** Connected to system ground through ferrite bead - technically connected to those capacitors as well.		** Connected to system ground through ferrite bead - technically connected to those capacitors as well.
		+
		+
		+	== Expansion Ports ==
		+
		+	[[File:Teensy4.1_computer_expansion_ports.png\|caption\|Expansion port layout, not including the card connector port\|800px]]
		+
		+	There are three large expansion ports on the Teensy 4.1 computer board, and 5 smaller ports. Here is a list, describing what each one breaks out:
		+	* Largest expansion port on the back of the board (J11)
		+	** Designed for large expansions to the computer system
		+	** Exposes all power pins, including VIN, 5v, 3.3v, GND, and even the Teensy's VBAT line
		+	** Numerous Teensy 4.1 pins: 0, 1, 11, 12, 13, 18, 19, 28, 29, 40, 41
		+	*** UART1
		+	*** UART7
		+	*** SPI0
		+	*** I2C0
		+	*** Analog inputs: A4, A5, A16, A17
		+	*** CRX2 and CTX2
		+	** '''3.3v-compatible''' 8-bit parallel bus
		+	*** Particularly useful for LCD displays and LCD display controllers, or any other parallel peripheral, for very high speeds
		+	* Right-side expansion port (J10 - reference not shown on board revision 1.1)
		+	** Designed for ATX-compatible expansions to the board
		+	** Exposes 5v and 3.3v lines
		+	** '''3.3v-compatible''' 8-bit parallel bus
		+	** Several Teensy 4.1 pins: 6, 7, 8, 9, 18, 19, 32
		+	*** UART2
		+	*** I2C0
		+	*** Analog inputs: A4, A5
		+	* Card Expansion Port
		+	** Provides a '''5v-compatible''' 8-bit parallel port. The pins are shared with the other parallel ports. The port is '''not bidirectional'''
		+	*** Controlled by write, read, and select lines. Select pin is pin 9, pulling it low will enable communication.
		+	** Provides only a 5v line.
		+	* I2S Expansion Port
		+	** Provides an alternative to the 3.5mm audio output, and allows one to attach a microphone
		+	** Breaks out I2S port 2
		+	** Can be used to add a microphone alongside use of the 3.5mm audio jack
		+	** Provides all power rails: VIN, 5v and 3.3v.
		+	** Breaks out pins 16 and 17
		+	*** I2C1
		+	*** Analog pins A2 and A3
		+	*** UART4
		+	*

@@ Line 36: / Line 36: @@
 == The Audio Circuit ==
-[[File:Teensy41_Computer_Audio_circuit.png|thumb|Teensy 4.1 Computer audio circuit]]
+[[File:Teensy41_Computer_Audio_circuit.png|thumb|Teensy 4.1 Computer audio circuit|600px]]
 The Teensy 4.1 is connected to the audio circuit via the Teensy's I2S 2 port.  This connection goes to the PCM5102 ADC.  As is recommended in the PCM5102's datasheet, filtering is added to the output, however the filter used on this board is a bit stronger, using a 4.7nF capacitor instead of the 2.2nF capacitor recommended in the datasheet.  The filter cutoff is still far above human perception, at 72kHz, and should filter high frequency noise a bit better.  The connection to the OPA1688 is DC, not AC, coupled, but this is according to the recommendations in the OPA1688 datasheet.  The gain of the amplifier is configured to be 1, so the output voltage of the amp should match the ADC's output voltage, and be in the range of 0v to 3.3v.  A voltage divider is used to activate the PCM5102's soft mute function when the 5v line drops, which is designed to prevent any pops in the audio when the power is disconnected.
@@ Line 77: / Line 77: @@
 == USB Ports ==
-[[File:Teensy4.1_computer_USB_schematic.png|thumb|Teensy 4.1 Computer USB circuit]]
+[[File:Teensy4.1_computer_USB_schematic.png|thumb|Teensy 4.1 Computer USB circuit|600px]]
 The Teensy 4.1's builtin USB port is connected directly to a TUSB2046 IC, which is a USB hub and provides four downstream ports.  Each port has overcurrent protection, with a maximum allowed current of 1.5A.  There are also TVS diodes on all USB data lines on the downstream ports, provided by three TPD3E001DRLR ICs.  Other than that, each downstream USB port has two 15k pulldowns - one on each data line.