PiPicoMite02

Features

• Raspberry Pi Pico
  • All Pico pins brought to headers
  • Pico pin marking on rear
• VGA
  • 640x480 monochrome resolution
  • 320x240 colour resolution
  • 1:2:1 - R:G:B - 16 colours
• PS/2 Keyboard
  • 5V to keyboard with voltage translator
  • Does not require a keyboard that runs at 3.3V
• SD Card
  • Full size card
  • Up to 32GB
  • FAT32 format
• Stereo audio
  • PWM with filter
  • 3.5mm jack
• 32-bit GPIO
  • 2xMCP23017 port expander
  • I2C1 (I2C2 from MMBASIC)
  • DB-37 Female connector
  • Jumper selectable terminators
• Power options
  • 5V power input
    • USB Micro on Pico card
    • USB B
    • 0.1" pitch header
  • 3.3V output header
• 95mmx95mm outline ODAS standard
• (4) 6-32 Mounting holes

BASIC Interpreter

The PicoMiteVGA boots straight into the MMBasic prompt. At which point you can enter, edit and save the program, test BASIC commands and run the program.

MMBasic is a Microsoft BASIC compatible implementation of the BASIC language. It is full featured with floating point, 64-bit integers and string variables, long variable names, arrays of floats, integers or strings with multiple dimensions, extensive string handling and user defined subroutines and functions. Typically it will execute a program up to 100,000 lines per second. Embedded compiled C programs can be used for even higher performance.

Using MMBasic you can use communications protocols such as I2C or SPI to get data from a variety of sensors. You can save data to an SD card, measure voltages, detect digital inputs and drive output pins to turn on lights, relays, etc.

The emphasis with MMBasic is on ease of use and development. The development cycle is very fast with the ability to instantly switch from edit to run. Errors are listed in plain English and when an error does occur a single keystroke will invoke the built in editor with the cursor positioned on the line that caused the error.

Pinout

Pin Marking on Rear

Schematic

• PiPicoMite01 Rev 1 Schematic

Connectors

J1 - I2C (RTC, etc.)

1. INT (GP3)
2. SCL (GP1)
3. SDA (GP0)
4. VCC
5. GND

Can use Real Time Clocks using the PCF8563, DS1307, DS3231 or DS3232 chips means that the time is always accurately known.

J2, J3 Pico Connectors

Pico Function Mapping

GP	FUNCTION	PICO PIN		GP	FUNCTION	PICO PIN
GP0	I2C1_INT (MCP23017)	1		GP16	VGA_HSYNC	21
GND	AUDIO-GND	8		GP17	VGA_VSYNC	22
GP6	AUDIO-L	9		GP18	VGA_BLU	24
GP7	AUDIO-R	10		GP19	VGA_GRN_LO	25
GP8	PS2_CLK	11		GP20	VGA_GRN_HI	26
GP9	PS2_DATA	12		GP21	VGA_RED	27
GP10	SD_SCK	14		VSYS	PS2_5V	39
GP11	SD_MOSI	15		3.3V	PS2_3.3V
GP12	SD_MISO	16		3.3V	SD_3.3V
GP13	SD_SLVSEL	17
GP14	I2C1_SDA (MCP23017)	19
GP15	I2C1_SCL (MCP23017)	20

J4- MCP23017s - I2C Interrupt 2

• Install jumper to connect INTA interrupts from MCP23017s to GP2 on Pico
• No Pull-up

J5 - I2C2 Terminators

• Install shunts to terminate SDA, SCL signals
• Commands

SETPIN GP14, GP15, I2C2
I2C2 OPEN 400, 100
I2C2 WRITE &H20, OC, LEN, B0[, B1...]
I2C2 READ &H20, OX, LEN, BUFF()

• &H20 - I2C Address 0x20
• OC: 0=terminate after, 1=chain next
• len - Length of buffer (normally 1 for receive)
• B0,B1... Bytes to send
• BUFF() - receive buffer

J6 - 3.3V Power Out

J7 - 5V Input

• Useful for external 5V

J8 - Audio

• Two Tone Test
• Play a WAV file

OPTION AUDIO GP6, GP7
PLAY WAV "file.wav"

J9 - VGA

The VGA output is 640 x 480 pixels in monochrome mode or 320 x 240 pixels in colour mode with 16 colours (1 bit for red, 2 bits for green and 1 bit for blue). The VGA output is generated using the second CPU on the RP2040 processor plus one PIO channel so it does not affect the BASIC interpreter which runs at full speed on the first CPU. A handfull of components (resistors and a couple of diodes) is all that is required to connect the VGA monitor.

From within your BASIC program you can turn pixels on/off and draw lines, boxes and circles in any colour. Text can be positioned anywhere on the screen and displayed in any colour in a variety of fonts.

The built-in editor within MMBasic works perfectly with the VGA monitor and PS2 keyboard to allow programs to be edited (with colour coded text) and saved to an SD card.

J10 - USB B Power Connectors

• Full size USB B connector
• No USB signal connections, just used for power

J11 - PS/2 Keyboard

The PS2 keyboard connects to the Raspberry Pi Pico via a level shifter and works as a normal keyboard with the function keys and arrow keys fully operational. It can be configured for the standard US layout used in the USA, Australia and New Zealand or specialised layouts used in the United Kingdom, Germany, France and Spain.

P1 - 32-bit GPIO

SetPin GP14, GP15, I2C2
I2C2 OPEN 400, 100
I2C2 WRITE &H20, 0, 2, &H00, &H00
I2C2 WRITE &H20, 0, 2, &H01, &H00
I2C2 WRITE &H21, 0, 2, &H00, &H00
I2C2 WRITE &H21, 0, 2, &H01, &H00

SD1 - SD Card

The PicoMiteVGA firmware reserves eight program storage "slots" in the Raspberry Pi Pico flash memory. Programs can be saved and retreived from these without the need for any additional storage.

For more storage SD cards can be connected with full support for these built into MMBasic including the ability to open files for reading, writing or random access and loading and saving programs. SD cards connect directly to the Raspberry Pi Pico and the firmware will work with cards up to 32GB formatted in FAT16 or FAT32. The files created can be read and written on personal computers running Windows, Linux or the Mac operating system.

OPTION SDCARD GP13, GP10, GP11, GP12

Mechanicals

PicoMite Software

PicoMite Source code

• PicoMite Source code
• Extra/replacement files for VGA

MCP23017 I2C Demo Code

• PROTO16-I2C card
• PIO16-01.BAS - GitHub repo
• MCP23017 Datasheet
• Set all 16 GPIO pins as outputs
• Write alternate patterns, bounce a 1 across the outputs

SetPin GP14, GP15, I2C2
I2C2 OPEN 400, 100
I2C2 WRITE &H20, 0, 2, &H00, &H00
I2C2 WRITE &H20, 0, 2, &H01, &H00
I2C2 WRITE &H20, 0, 2, &H14, &H55
I2C2 WRITE &H20, 0, 2, &H15, &HAA
Pause 1000
I2C2 WRITE &H20, 0, 2, &H14, &HAA
I2C2 WRITE &H20, 0, 2, &H15, &H55
I2C2 CLOSE

MCP23008 Demo Code

• I2CIO-8 card
• MCP23008 Datasheet
• I2CIO8-Bounce.bas - GitHub repo
  • Bounce a bit across the 4 LEDs
• I2CIO8-ReadWrite.bas - GitHub repo
• Read 4 jumpers and write out LEDs

Tetris

> memory
Program:
  13K (10%) Program (485 lines)
  95K (90%) Free

RAM:
   8K ( 5%) 31 Variables
   0K ( 0%) General
 132K (95%) Free

Issues

Rev 1

• SDA, SCL swapped to MCP23017
• Cut etch solder side U2-12
• Cut etch solder side U2-13
• Add wire Pico pin 19 to U2-13 (GP14) (or etch that went to Pico pin 20)
• Add wire Pico pin 20 to U2-12 (GP15) (or etch that went to Pico pin 19)

Assembly Sheet

• PicoMite02 Rev1 Assembly Sheet
• PiPicoMite02 Rev1 Assembly Sheet