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)

QTPy49-01 Card

The QTPy49-01 Card combines the QTPy49 card and SD_CARD_X49 card onto one card
Headers for other pins
DC in jack with 5V regulator and Schottky diode
Power can be supplied from DC in (7-12V) or USB Jack

QTPy49 / SD Card Set

QTPy49 breakout card

QTPy49 Wiki page

QT Py (RP2040 based) CPU choices are
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 GP1, GP0

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