BBC micro:bit MicroPython TM1637

A micro:bit MicroPython library for quad 7-segment LED display modules using the TM1637 LED driver.

For example, the Grove - 4 Digit Display module

Installation

• Install MicroPython for micro:bit by either compiling from source or using one of the included precompiled firmwares
• Install ufs to upload .py scripts
• Copy tm1637.py and one of the example main.py scripts to the micro:bit
• Reset to run main.py on boot.

Examples

There are multiple methods which can produce the same result. Here are a few examples to get you started.

from microbit import *
from tm1637 import TM1637
tm = TM1637(clk=pin1, dio=pin2)

# all LEDS on "88:88"
tm.write([127, 255, 127, 127])
tm.show('8888', True)
tm.numbers(88, 88)

# all LEDS off
tm.write([0, 0, 0, 0])
tm.show('    ')

# write to the 2nd and 3rd segments only
tm.write([119, 124], 1)
tm.write([124], 2)
tm.write([119], 1)

# display "0123"
tm.show('1234')
tm.number(1234)
tm.numbers(12, 34)

# show "COOL"
tm.write([0b00111001, 0b00111111, 0b00111111, 0b00111000])
tm.write([0x39, 0x3F, 0x3F, 0x38])
tm.write([57, 63, 63, 56])
tm.show('cool')
tm.show('COOL')

# display "dEAd", "bEEF"
tm.hex(0xdead)
tm.hex(0xbeef)
tm.show('dead')
tm.show('Beef')

# show "12:59"
tm.numbers(12,59)
tm.number(1259, True)
tm.show('1259', True)

# show "-123"
tm.number(-123)
tm.show('-123')

# show temperature '24*C'
tm.temperature(24)
tm.show('24*C')

# get current brightness
tm.brightness()

# reduce brightness
tm.brightness(3)

For more detailed examples, see /examples.

Seven Segment Font

They are called 7-segment displays as there are 7 LEDs for each digit (segment). One byte (7 lower bits) for each segment. The 8th bit (MSB) is for the colon and only on the 2nd segment.

      A
     ---
  F |   | B   *
     -G-      H (on 2nd segment)
  E |   | C   *
     ---
      D

  HGFEDCBA
0b01101101 = 0x6D = 109 = show "5"

Display	Bin	Hex	Dec
0	0b00111111	0x3F	63
1	0b00000110	0x06	6
2	0b01011011	0x5B	91
3	0b01001111	0x4F	79
4	0b01100110	0x66	102
5	0b01101101	0x6D	109
6	0b01111101	0x7D	125
7	0b00000111	0x07	7
8	0b01111111	0x7F	127
9	0b01101111	0x6F	111
A	0b01110111	0x77	119
b	0b01111100	0x7C	124
C	0b00111001	0x39	57
d	0b01011110	0x5E	94
E	0b01111001	0x79	121
F	0b01110001	0x71	113
G	0b00111101	0x3D	61
H	0b01110110	0x76	118
I	0b00000110	0x06	6
J	0b00011110	0x1E	30
K	0b01110110	0x76	118
L	0b00111000	0x38	56
M	0b01010101	0x55	85
n	0b01010100	0x54	84
O	0b00111111	0x3F	63
P	0b01110011	0x73	115
q	0b01100111	0x67	103
r	0b01010000	0x50	80
S	0b01101101	0x6D	109
t	0b01111000	0x78	120
U	0b00111110	0x3E	62
v	0b00011100	0x1C	28
W	0b00101010	0x2A	42
X	0b01110110	0x76	118
y	0b01101110	0x6E	110
Z	0b01011011	0x5B	91
blank	0b00000000	0x00	0
-	0b01000000	0x40	64
*	0b01100011	0x63	99

Methods

Get or set brightness.

brightness(val=None)

Write one or more segments at a given offset.

write(segments, pos=0)

Convert a string to a list of segments.

encode_string(string)

Convert a single character to a segment.

encode_char(char)

Display a number in hexadecimal format 0000 through FFFF.

hex(val)

Display a number -999 through 9999, right aligned.

number(num)

Display 2 independent numbers on either side of the (optional) colon, with leading zeros.

numbers(num1, num2, colon=True)

Display a temperature -9 through 99 followed by degrees C.

temperature(num)

Show a string on the display. Shorthand for write(encode_string()). Limited to first 4 characters.

show(string, colon=False)

Display a string on the display, scrolling from the right to left, speed adjustable. String starts off-screen and scrolls until off-screen at 4 FPS by default.

scroll(string, delay=250)

Parts

• BBC micro:bit $24.95 AUD
• Edge Connector Breakout Board $11.95 AUD
• Grove 4 Digit Display $5.90 USD
• Grove Male Jumper Cable $2.90 USD

Connections

micro:bit	Grove 4 Digit Display
Pin 1	CLK (yellow)
Pin 2	DIO (white)
3V3	VCC (red)
GND	GND (black)

An edge connector breakout board comes in handy here.

You're welcome to change the data and clock pins to something else - just update TM1637(clk=pin1, dio=pin2) in your main.py

Links

• BBC micro:bit
• MicroPython for the BBC micro:bit
• Kitronik Edge Connector Breakout Board
• Grove 4 Digit Display Wiki Page
• micropython.org
• micro:bit on the MicroPython forum
• microfs
• TM1637 datasheet
• Titan Micro TM1637 product page
• MicroPython TM1637

Troubleshooting

If you upload a new .hex file, all changes are overwritten and you will need to ufs put both the tm1637.py and main.py scripts again.

If you edit one of the example precompiled .hex files in one of the online editors, it may swap the MicroPython runtime to an older version and introduce bugs. Best to flash one of the stock MicroPython firmwares and upload your own tm1637.py and main.py scripts.

If you flash a .hex file from an online editor, it may block main.py from running as the editor combines the MicroPython runtime with your script. Your script is executed like the main script, however, you can't ufs get and ufs put changes.

If you board is throwing MemoryErrors and you are unable to continue, start fresh by copying one of the MicroPython firmware .hex files to the MICROBIT mounted filesystem.

License

Licensed under the MIT License.