MMBASIC on XIAO RP2040

Overview

• Card set running BASIC Interpreter for the Raspberry Pi Pico on Seeed Studio XIAO RP2040
• MMBasic is a Microsoft BASIC compatible implementation of the BASIC language with floating point, integer and string variables, arrays, long variable names, a built in program editor and many other features
• 8 Flash locations for storage.
• Support for SD Card

MMBASIC Credits

Peter Mather led the project, ported the MMBasic interpreter to the Raspberry Pi Pico and wrote the hardware device drivers. Geoff Graham wrote the MMBasic interpreter and the manual. Mick Ames wrote the PIO compiler and its corresponding documentation.

Hardware

• Seeed Studio XIAO RP2040
• 1-2 card set
  • QTPy49-01 breakout card with SD card
  • RS-232 serial card (optional)
• 2-3 card set
  • QTPy49 breakout card
  • SD Adapter card
  • RS-232 serial card (optional)

Seeed Studio XIAO RP2040

QT_Py_(RP2040_based) Wiki page

• Two manufacturers
  • Adafruit QT Py RP2040 Product page
  • Seeed XIAO RP2040 Product page
• USB Type C connector
• RP2040 32-bit Cortex M0+ dual-core
• Runs at ~125 MHz
• 264 KB RAM
• SPI FLASH chip for storing files and CircuitPython/MicroPython code storage
  • 8 MB - Adafruit
  • 2 MB - Seeedstudio
• No EEPROM
• Can be used with C/C++ (Arduino), MicroPython, or CircuitPython
• Built-in RGB NeoPixel LED
• 13 GPIO pins (11 breakout pads and two QT pads):
  • Four 12 bit ADCs (one more than Pico)
  • I2C port
    • 2 I2C: 1 on QT pins, one on the (Adafruit) breakout pads - Adafruit
    • 1 I2C on XAIO
  • SPI and UART peripherals, in standard QT Py locations,
  • PWM outputs on every IO pin - for servos, LEDs, etc
  • There are 6 GPIO in consecutive order for PIO compatibility
• 3.3V logic and power 600 mA
• Both Reset button and Bootloader select buttons for quick restarts (no unplugging-replugging to relaunch code)

QTPy49 / SD Card Set

QTPy49 breakout card

QTPy49 Wiki page

• QT Py (RP2040 based) CPU choices are
  • Adafruit QT Py RP2040 Product page
  • Seeed XIAO RP2040 Product page
  • 133 MHz
• Connectors/Headers
  • DC Power
  • AD0 GVS
  • AD1 GVS
  • AD2 GVS
  • AD3 GVS
  • I2C with ground/VCC
  • TX/RX with ground/VCC
  • SPI with ground/VCC
• QTPy49 can be powered from with either the USB C or DC jack
  • Automatic Schottky diode power switching between
    • 5V from USB C
    • 5V on external DC jack
    • 7-12V on DC jack
• 49x49mm ODAS form factor
• (4) 4-40 mounting holes

SD Card

SD_CARD_X49 wiki page

• SD or SDHC card adapter
• 5V to 3.3V regulator
• 3.3V to 5V TXS0104E level shifter
• Activity LED
• 49 x 49 mm ODAS foprm factor
• (4) 4-40 mounting holes

SD Card Wiring

• SD_CARD_X49 card
  • NO5V jumper installed

Signal	SD_CARD_X49	QTPy49 conn	QTPy GP	PiPico Pin
SPI_SCLK	J1-3	J3-6	GP2	GPIO2
SPI_MOSI	J1-4	J3-4	GP3	GPIO3
SPI_MISO	J1-2	J3-5	GP4	GPIO4
SPI_SS	J1-5	J9-3	GP26	GPIO26
GND	J1-1	J9-1	GND	GND
VCC (3.3V)	J1-7	J9-2	VCC	VCC

SD Configuration

OPTION SYSTEM SPI GP2, GP3, GP4
OPTION SDCARD GP26
OPTION COLOURCODE ON

• Verify it is working

> FILES
A:/
   <DIR>  basic
   <DIR>  bmps
   <DIR>  demos
   <DIR>  games
   <DIR>  jpegs
   <DIR>  lbcards
   <DIR>  performance
   <DIR>  wave
8 directories, 0 files

RS-232 (option)

DTE wiki page

• TTL to RS-232 converter
• Male DB-9 connector
• FTDI pinout (reversed directions to directly connect to FTDI Interface)
• 49x49mm card
• 4x 4-40 holes
• DTE card

Command to use serial as console

• • 115,200 baud = default

OPTION SERIAL CONSOLE GP0, GP1

• Command to use serial as console switch back from the serial port to the USB on the XIAO RP2040

option serial console disable

User Serial port

• Command to use serial as COM port

setpin gp1,gp0, com1
open "com1:9600" as #5
print #5, "Hello"

RS-232 Wiring

• Wiring to DTE card

DTE signal	DTE pin	QTPy GP	PiPico Pin
GND	H1-1	GND	J4-1
CTS	H1-2	N/C	N/C
VCC	H1-3	VCC	J4-2
TX	H1-4	TX_D6	J4-3
RX	H1-5	RX_D7	J4-4
RTS	H1-6	N/C	N/C

• Wiring to FTDI-49MM card
  • Swap TX/RX pins

RS-232 Stackup

RS-232 to USB

• Uses FTDI-49MM FTDI to TTL card
• RS-232 to USB
• Mates to CPU stackup

• Brought all the way back to USB

MMBASIC Card Stack-up

Software

Install MMBASIC on Seeed XIAO RP2040

• Hold down the "BOOT" button
  • The "B" is written on the board shown to the right
• Connect the XIAO RP2040 via USB C cable to your computer while still pressing the button
• The computer then will appear a disk driver(RP1-RP2)
• Download the PicoMite_Firmware.zip
• Drag the .uf2 file to the disk drive ("RP1-RP2")
• Card will re-boot
• Connect in TeraTerm over serial

MMBASIC Free Memory

• V5.070501

> print mm.ver
 5.0704
> memory
Program:
   0K ( 0%) Program (0 lines)
 124K (100%) Free

RAM:
   0K ( 0%) 0 Variables
   0K ( 0%) General
 156K (100%) Free

GPIO from MMBASIC

QTPy49 Marking	GPIO
A0	GP26 (SD_SS)
A1	GP27
A2	GP28
A3	GP29
I2C_SDA	GP6
I2C_SCL	GP7
RX	GP1
TX	GP0

MMBASIC - Using Pins

• Digital I/O

SETPIN GP27, DIN:' Digital Input
SETPIN GP28, DOUT:' Digital Output
PIN(GP28) = 1:'Digital output

• Analog Input

SETPIN GP29, AIN:' Analog Input

• SETPIN(s) for Serial and I2C

SETPIN GP1, GP0, COM1
SETPIN GP6, GP7 I2C2

On-Board LED

• No Built-in support in MMBASIC for the on-board NEOPIXEL
• Red, Green, Blue LED
• Pull Low to turn on RGB LED bits
• At-boot - RGB LED blinks Cyan/Green by MMBASIC
• Red LED = GP17
• Green LED = GP16
• Blue LED = GP25 (Used by MMBASIC)

' Make pins outputs
SETPIN GP17, DOUT:' Red LED
SETPIN GP16, DOUT:' Green LED
SETPIN GP25, DOUT:' Blue LED
' Turn off LEDS
PIN(GP17)=1:' Turn off Red LED
PIN(GP25)=1:' Turn off Blue LED
PIN(GP16)=1:' Turn off Green LED
' Turn on LEDs
PIN(GP17)=0:' Turn on Red LED
PIN(GP25)=0:' Turn on Blue LED
PIN(GP16)=0:' Turn on Green LED

Demo Code

• SD Card contents
  • PROTO16_LEDs.bas
    • Bounces a bit across the PROTO16-I2C card