Basic on a Raspberry Pi Pico

                            Or, yet another clock.

But First - some history (nostalgia).

The IBM PC released in August 1981
Purchased Dec. 1984
When you booted this thing without disks it booted into "Cassette Basic"
Ram Memory: 16Kb to 640Kb Max
320Kb per Disk
Cpu Speed:
4.77 MHz
~$6000 No Tax or shipping - includes software and printer ($17,000 today)

Pi Pico released in January 2021
Purchased January 2021
When you boot this it boots into MMBasic a "clone" of Microsoft Basic
Ram Memory:
Cpu Speed
125MHz dual core
$10 with tax and shipping



  1. Download the firmware (includes the Amazing Documentation above) from to a new directory of your choice - perhaps picoBasic.
  2. Unzip the downloaded file.
  3. Hold down the boot button on the Pico and plug in the USB cable to the computer that you downloaded the firmware file.  This will present the Pico as a remote disk.
  4. Copy the file PicoMiteV5.07.04.uf2 (your version may vary) to the "remote disk".
  5. When the copy is done the Pico will reboot and the onboard Led will start to blink.

Connect a terminal (Gnome Terminal) to the Pico

I have the Pico connected to a Raspberry Pi USB port. The Pico shows up as /dev/ttyACM0. It's complicated.  Basically it depends on how the device presents itself

To connect my terminal app to the desired tty use:

screen /dev/ttyACM0

Hello World

print "hello,  world"

A loop

Because the first time I saw a loop in a computer language I was beside myself with excitement.

for num = 0 to 20 step 2
    print num
next num

Blink Led - of Course

Pico Pinouts
 Because we need a pin to attach a Led

' Loop blinking led

SetPin gp21, dout

    Pin(gp21) = 1
    Pause (300)
    Pin(gp21) = 0
    Pause (700)

And then a perfect example of scope creep

It started out with hello world.  Then flashing a led then measuring temperature and displaying it on the terminal, because that was easy.  Next displaying the time and temperature on the terminal, because one needs to know when. 

Then a Oled screen to show the time and temperature.   But still I needed to enter the time on boot. So I needed to add a real time clock. Next a distance sensor and a PIR detector.  And, last a SD card reader writer.

And it was all easy Geoff Graham and folks have done an amazing job on this software and documentation.

(not the breadboard below - that's my fault)

Introducing the FrankenBoard ...

Save/load programs

There are 7 flash storage locations for programs 1-7.
Some of the FLASH commands:

Read and display temperature 


Simply: PRINT "Temperature: " TEMPR(pin)

For my system:
 print Tempr(gp20)

Read and display temperature and blink

' Blink loop, temperature

Print "hello blinking world.  The temperature:"
SetPin gp21, dout

  Pin(gp21) = 1
  Pause 300
  Pin(gp21) = 0
  Pause 700
  Print TEMPR(gp20)
And then time and temperature ...
  Pin(gp21) = 1
  Pause 300
  Pin(gp21) = 0
  Pause 700
  print TIME$
  Print TEMPR(gp20)

But if it is not hooked to a computer display on an SSD1306 Oled display.

Set the I2C pins and  choose the desired Led panel.
From the documentation:
"Initialises a OLED display using the SSD1306 controller with an I2C interface. This supports 128 * 64 resolution. An additional parameter offset may be specified to control the position of the display. 0.96" displays typically need a value of 0. 1.3" displays typically need a value of 2. Default if omitted is 0. NB many cheap I2C versions of SSD1306 displays do not implement I2C properly due to a wiring error. This seems to be particularly the case with 1.3" variants"

For my system:
option system i2c, 1, 2 
option lcdpanel ssd1306i2c, landscape
When you execute the above commands the pico will reboot - for both of the commands.

The Y.A.C. (yet another clock)

' Set the font size and clear the Oled screen
Font 2

' Subroutine to blink the led
Sub blink ontime, offtime
  Pin(gp21) = 1
  Pause ontime
  Pin(gp21) = 0
  Pause offtime
End Sub

' Print hello and set the led pin to output
Print "hello cool world.  The temperature is:"
SetPin gp21, dout

' Loop forever ^C will stop
  ' Blink the led
  blink(300, 700)

  ' Display the time and temperature
  Print "Time: " + Time$
  ' Get the temperature and adjust
  t = TEMPR(gp20) + 3
  ts$ = Str$(t, 0, 2)
  Print "Temperature: " + ts$

  ' Display the time and temperature on the Oled
  Text 5, 0, Time$
  Text 20, 25, ts$

DS3231 Real Time Clock

We don't want to have to enter the time on boot.  No additional code is required.  Just turn on the option to read the RTC on boot.  This will initialize the time$ system variable when the Pico is booted.

option rtc auto enable
I was a bit nervous about adding the RTC since both the Oled and the RTC are I2C devices and nowhere are addresses specified.  I guess MMBasic figures it out from the addresses presented.

SSD1306 SH1106 PCF8569 PCF8578 PCF8574AP SSD1305

SSD1306 SH1106 PCF8578 PCF8574AP SSD1305
PCA9685 AMG8833 DS1307 PCF8523 DS3231 MPU-9250 ITG3200 PCF8573 MPU6050 ICM-20948 WITTY PI 3 MCP3422 DS1371

HC-SR04 ultrasonic sensor

and the command to read it is

distance(trigger pin,  echo pin)

on my system:
distance(5, 4)

Craig wanted a Passive Infrared  motion detector
(PIR) HC-SR501

 HC-SR501 Module

The battery so it can run stand alone

The Pico will run from 1.8V to 5.5V.  An onboard Switched Mode Power Supply (SMPS)  will condition this to the required 3.3V.  The battery connects to the VSYS pin which feeds the SMPS.

Now I had to measure the voltage on the battery.  The VSYS voltage/3 is available via an analog input on pin 44 
print Pin(44) * 3

SD Card reader/writer

Wire it up and set the following options.  They will cause the Pico to reboot.



> files
12:44 24-10-2022         63  prog1.bas
12:44 24-10-2022        126  prog2.bas
12:45 24-10-2022        190  prog3.bas
12:45 24-10-2022        668  prog4.bas
12:41 24-10-2022       2405  prog6.bas
0 directories, 5 files

> chdir ".."
> files
   <DIR>  basic
00:04 28-09-2022        204  blink.bas
21:31 17-10-2022         48  loop.bas
12:24 24-10-2022       2405  prog6.bas
17:26 13-10-2022        230  tblink.bas
17:24 13-10-2022        655  yac.bas
1 directory, 5 files

> list "blink.bas"
Option autorun on
Option colourcode off

Sub blink ontime, offtime
  Pin(gp21) = 1
  Pause ontime
  Pin(gp21) = 0
  Pause offtime
End Sub

Print "hello world"
SetPin gp21, dout

  blink 300, 600
> load "loop.bas"
> list
For num = 0 To 20 Step 2
    Print num
Next num


Since I have an SD card to put stuff on, why not save the battery voltage for a while.  In this case until the Pico stops.

Nickel Metal Hydride (NiMH) two AA cells. 

                 From a newly charged battery until the Pico stops.


Transfer Files from/to a host computer

We are going to use sx (xmodem send) to get a file from the host to the Pico

You may have to install sx. 
apt install lrzsz
Then on the Pico terminal:
  1. xmodem receive
  2. Ctrl A :  No spaces - to enter command line mode
  3. exec !! sx filetoupload

    (If anyone can parse what what the !! is doing in this statement...??)

Am I Done?

Maybe, but I have some photo resistors, neo pixel leds, buzzers and relays ...


The following options have been set to enable the behaviour that has been discussed

Misc. Links