This board is for a TRS-80 Model 100/102/200 sound card that uses the ubiquitous Yamaha YM3812 and plugs directly into the LPT port on the Model T. It requires an external +5V “clean” power supply, a mini-USB port or header pins are provided for this purpose. Use of a good quality supply is recommended as any power supply noise will impact the audio quality. The audio jack is intended to allow the use of headphones or an external speaker. The max gain on the board is limited due to a single +5v supply rail. The trimpots can be used to set the:

*‘Volume’ (the range is limited due to the power supply) for optimum performance with the external speaker.

*‘Bass Boost’ (if installed) can be used to enhance the lower frequencies.

*‘Gain’ (if installed) is used to alter the gain of the Audio amp.

Link 1 and Link 2 can be used to configure the board for use with other parallel port devices. On the Model T link 1 should be shorted and Link 2 can be left open. The reset button is used to reset the device.

All the parts are readily available and through hole to make assembly relatively easy. A simple BASIC driver is required to convert the LPT port into a parallel port to drive the unit.

Materials

All the ICs should be socketed make it easier to debug in case of any issues.

DigiKey Parts

Digikey Parts list Digikey is used to list some parts however other suppliers might have lower prices.

eBay Parts

U3 YM3812

U4 YM3014B

Jameco Parts

*C10, C15- deleted.

Resistors

All the resistors are generic 1/8W through hole parts and can be sourced any where.

Note: The parts lists in some cases includes more than is required for one board this is due to the lower overall price for a larger quantity.

PCB for turnipschool taken from https://github.com/mossmann/cc11xx/tree/master/turnipschool

Amiga Bootselector using THT TTL ICs Version 3

Black Mesa Labs 3A DC/DC Switcher in TO-220 footprint using the BD9C301FJ. Wide input voltage and output voltage ranges.

Fixed version of the Black Mesa Labs PAM2305D based 1A DC/DC converter.

Hall Latch, 3.5V to 24V, Melexis US1881

Two of these will be able to make a quadrature encoder with North and South facing magnets. The US1881, us1881-datasheet-melexis.pdf, is a latching device requiring the opposite pole to unlatch/latch. R1 (SMT 1206) is 10K and must be rated for the voltage you use. These do work at 3.3 volts.

Note (180314): This board has been tested and found to be working according to expectations! Correction of some minor design flaws is underway! A new but untested design is available here: https://oshpark.com/shared_projects/uIL9j2Ex

The quick and dirty mockup code is available here: https://github.com/overengen/Pedestrian_Crossing_for_the_RPi

Warning! This board hasn’t been tested yet, but the mock-up did work as intended but there might still be issues that needs to be addressed such as the “be or not to be” capacitor placed over the buzzer. And then there is this tiny detail about the order of LEDs and resistors… Mounting holes are missing, and the board might be ½ mm to short. Watch out for future revisions!

This is my first attempt to design a PCB for the Raspberry Pi. It’s a dead simple design and supposed to fit on top of a Raspberry Pi (65x56.5mm). With a bit of coding the Raspberry Pi should be able to control all the LEDs, the buzzer and read the push button. My intention is to use this as a base for a coding project at school. Pin numbers (connecting to the switch, the buzzer and the LEDs) are written on the surface of the PCB as a reference in order to make coding a bit easier.

BOM:

3 x 10mm LEDs (red, yellow, green).

2 x 5mm LEDs (red, green).

1 x 3mm LED (yellow or white).

1 x Switch 4pins, 6mm.

1 x Buzzer

6 x Resistors (~50 Ohm)

1 x Connector (20x2)

Warning! This board hasen’t been tested yet, there might still be issues that needs to be addressed. Watch out for future revisions!

Note (180314): A previous and tested version of this design is available here: https://oshpark.com/shared_projects/wrF9XJDk

The quick and dirty mockup code is available here: https://github.com/overengen/Pedestrian_Crossing_for_the_RPi

The pin layout has been changed in this later revision of the PCB, but this is easily corrected in the program by swapping out a few numbers accordingly.

Update: v0.5 - Adjusted position af the mounting holes and dimensions around the corners that was slightly of and smaller in arc.

Update: v0.4 - Rearranged som of the graphic, redesigned the wiring and pinout to make them follow a more logical order and easier to use while programing.

GPIO Reference:

P20 - Red 10mm

P21 - Yellow 10mm

P22 - Green 10mm

P23 - Red 5mm

P24 - Green 5mm

P25 - White 3mm

P26 - Switch

P27 - Buzzer

This is my first attempt to design a PCB for the Raspberry Pi. It’s a dead simple design and supposed to fit on top of a Raspberry Pi (65x56.5mm). With a bit of coding the Raspberry Pi should be able to control all the LEDs, the buzzer and read the push button. My intention is to use this as a base for a coding project at school. Pin numbers (connecting to the switch, the buzzer and the LEDs) are written on the surface of the PCB as a reference in order to make coding a bit easier.

BOM:

3 x 10mm LEDs (red, yellow, green).

2 x 5mm LEDs (red, green).

1 x 3mm LED (yellow or white).

1 x Switch 4pins, 6mm.

1 x Buzzer

6 x Resistors (~50 Ohm)

1 x Connector (20x2)

attiny85 Programmer with ISP usbtiny programmer

Blog post - https://facelesstech.wordpress.com/2018/03/17/attiny85-backpack-programmer-header/ Youtube - https://youtu.be/_xBqEfxCav8 Github board files - https://github.com/facelessloser/attiny_85_programmer_header

50mil castelation ICSP jig for Northpaw Nano rev G

• ATMEGA328P-MU (or equiv 32-pin ATMEGA 328/168/etc in MLF footprint)
• MAX4822 (there is no alternative - not even in a different footprint or functionality - this is THE ONLY 3v 8channel PWM/PSAVE with kickback - let me know if you find another (other than MC33996, which is “technically” 5v - see my “Northpaw Mini” versions instead)
• MCP1700T-3002E/TT (or any pin-compatible 200mA 200mV sot-23 LDO)
• 0805 MLCC ceramic capacitors - 0.1uF, 0.22uF, 1uF, 10uF (x2)
• 0805 resistors - 10k ohm (x2) - (for voltage divider. use other values for better voltage granularity)
• LSM303DLHC (magnetometer/accelerometer - LGA)
• 8x 100mA motors
• Ribbon cable
• JST-PH connection to Li-Po/Li-Ion battery (or other 3.0v-6.0v battery pack)
• Optional 0805 LED & 0805 resistor for it (choose for however bright you want, e.g. 1k ohm)

All chips rated 2.3v-3.6v (lsm303 can go lower; and the rest are rated up to 5.5v - and all 85 deg C) lsm303: vdd 2.16v-3.6v; max4822: vcc 2.3v-5.5v; 328p: 2.7v-5.5v@8MHz (1.8v@4MHz)

Programming ICSP on custom pinout 50mil pitch castellation.

“Flora-compatible” mounting holes (random holes near edges, probably sewable)

Active power consumption: 100mA-50mA single motor; 6mA atmega; 1.5mA max4822; 150uA lsm303 (that can’t be right); sleep power consumption (after battery level low): 150uA (typ)/300uA(max) into MAX4822; 8uA into motors (leakage); 1uA into atmega (power-down with PRR off, WDT off, & BOD off); 1uA into lsm303 (so they say) so ~0.2mA after flat battery - so don’t leave it plugged in for weeks after shutdown or it will destroy the battery.

MLX10407 breakout board - essentially implements the example schematic in the datasheet. The specced crystal is the ACH-8.000MHZ-EK from ABRACON, but any 8MHz crystal should work.