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GY-63_MS5611/libraries/TM1637_RT/README.md
Rob Tillaart bbd5725e4d 0.3.7 TM1637_RT
2023-04-17 13:13:30 +02:00

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Arduino CI Arduino-lint JSON check License: MIT GitHub release

TM1637

Library for TM1637 driven displays and key scans.

Description

The TM1637 drives 7 segment displays and can also scan a 16 key keyboard.

Library is tested with Arduino UNO and a 6 digits display and 4 digit (clock) display.

ESP32 is supported since 0.2.0 see https://github.com/RobTillaart/TM1637_RT/pull/5

Related

Interface

#include "TM1637.h"

Core

  • TM1637() constructor
  • void begin(uint8_t clockPin, uint8_t dataPin, uint8_t digits = 6) set up the connection of the pins to the display. As the display is only tested with a 6 digit display, this is used as the default of the digits parameter.

Display functions

  • void displayPChar(char *buff) display the buffer. Experimental - Tested on STM32 and Arduino Nano
  • void displayRaw(uint8_t * data, uint8_t pointPos) low level write function.
  • void displayInt(long value) idem
  • void displayFloat(float value) idem, position of point may vary!
  • void displayFloat(float value, uint8_t fixedPoint) display float with fixed point position.
  • void displayHex(uint32_t value) idem
  • void displayClear() writes spaces to all positions, effectively clearing the display.
  • void displayTime(uint8_t hh, uint8_t mm, bool colon) displays time format. The function does not check for overflow e.g. hh > 59 or mm > 59. Works only on a 4 digit display.
    • hours + minutes HH:MM
    • minutes + seconds MM:SS
    • seconds + hundreds SS:hh
  • void displayTwoInt(int ll, int rr, bool colon = true) print two integers, one left and one right of the colon. The function allows a range from -9 .. 99 (not checked). The colon is default on as separator. Works only on a 4 digit display. Applications include:
    • temperature + humidity TT:HH (humidity to 99%)
    • heartbeat + oxygen HH:OO
    • meters + centimetre MM:CC (e.g distance sensor)
    • feet + inches FF:II
    • any pair of integers (-9 .. 99) side by side.
  • void displayCelsius(int temp, bool colon = false) print temperature Celsius. The function allows a range from -9 .. 99 + <20>C. The colon is default false. Works only on a 4 digit display. It can be used e.g. to indicate under- or overflow, or any other threshold.
TM.displayCelsius(temperature, (temperature < -9) || (temperature > 99));

Brightness

  • void setBrightness(uint8_t brightness = 3) brightness = 0 .. 7 default = 3.
  • uint8_t getBrightness() returns value set.

KeyScan

  • uint8_t keyscan(void) scans the keyboard once and return result. The keyscan() function cannot detect multiple keys.

DisplayRaw explained

displayRaw() can display multiple decimal points, by setting the high bit (0x80) in each character for which you wish to have a decimal lit.
Or you can use the pointPos argument to light just one decimal at that position.

displayRaw() can display some of the alphabet as follows:

  • space (blank) is 0x10
  • '-' (minus) is 0x11
  • a-f are coded as 0x0a-0x0f
  • g-z are coded as 0x12-0x25. Characters that cannot be represented in 7 segments render as blank. So "hello " is coded as 0x13, 0x0e, 0x17, 0x17, 0x1a, 0x10

displayPChar explained

void displayPChar(char * buff) Attempts to display every ASCII character 0x30 to 0x5F. See example TM1637_custom.ino to insert your own 7 segment patterns. Also displayed are ' ' , '.' and '-' . Decimal points may also be displayed by setting the character sign bit.

See routine ascii_to_7segment() in the example TM1637_keyscan_cooked.ino. It presents a more convenient interface for displaying text messages on the display.

Routine button_poll() in the same example shows one way of polling and de-bouncing button presses.

Obsolete (0.4.0)

  • void init(uint8_t clockPin, uint8_t dataPin, uint8_t digits = 6) replaced by begin().

Display support

The library is tested with a 6 (=2x3) digit - decimal point - display and a 4 (=1x4) digit - clock - display. At low level these displays differ in the order the digits have to be clocked in. To adjust the order for a not supported display, the following function can be used with care:

  • void setDigitOrder(uint8_t a, uint8_t b,... uint8_t h) sets the order in which up to 8 digits should be clocked in.

If you have a (7 segment) display that is not supported by the library, please open an issue on GitHub so it can be build in.

Tuning function

setBitDelay() is used to tune the timing of writing bytes. An UNO can gain up to 100 micros per call by setting the bit delay to 0. However some displays might fail with short bit delay's. Do not forget to use a pull up resistor on the clock and data line.

  • void setBitDelay(uint8_t bitDelay = 10)
  • uint8_t getBitDelay()

Tuning minimum pulse length

The class has a conditional code part in writeSync to guarantee the length of pulses when the library is used with an ESP32. The function called there nanoDelay(n) needs manual adjustment depending upon processor frequency and time needed for a digitalWrite. Feel free to file an issue to get your processor supported.

Keyboard Scanner usage and notes

Calling keyscan() returns a uint8_t, whose value is 0xff if no keys are being pressed at the time.
The TM1637 can only see one key press at a time, and there is no "rollover".
If a key is pressed, then the values are as follows:

keyscan results are reversed left for right from the data sheet.
pin 23456789
 namesg1sg2sg3sg4sg5sg6sg7sg8
19k10xf70xf60xf50xf40xf30xf20xf10xf0
20k20xef0xee0xed0xec0xeb0xea0xe90xe8

To modify a "generic" TM1637 board for use with a keyboard, you must add connections to either or both of pins 19 and 20 (these are the "row" selects) and then to as many of pins 2 through 9 (the "columns") as needed. It is easiest to connect to the "column pins" (2-9) by picking them up where they connect to the LED displays (see second photo). Generic keyboards that are a 4x4 matrix won't work; the TM1637 can only scan a 2x8 matrix. Of course, fewer keys are acceptable; I use a 1x4 keyboard in my projects.

Further, the TM1637 chip needs a fairly hefty pull-up on the DIO pin for the keyscan() routine to work. There is no pull-up in the TM1637 itself, and the clone boards don't seem to have one either, despite the data sheet calling for 10K ohms pull-ups on DIO and CLOCK. 10K is too weak anyway. The slow rise-time of the DIO signal means that the "true/high" value isn't reached fast enough and reliably enough for the processor to read it correctly. The new pull-up reduces the rise time of the signal, so that true/high values are achieved in a few microseconds. I find that a 1K (1000) ohm resistor from DIO to 3.3 v works well. This is perfect with a 3.3 volt processor like the ESP8266 or ESP32, and a 5V Atmega 328 ("Arduino UNO") family processor is happy with that as well.

The TM1637 boards want to be run off of 5 volts, regardless of what the processor voltage is. Their logic levels are compatible with 3.3 volt processors, and they need 5 volts to make sure the LEDs light up.

The unmodified generic TM1637 board (front and back).

The modified generic TM1637 board with connector for 1x4 keyboard. The blue wire is bringing out pin 19 (k1). Four segments/columns are picked up from the LEDs.

The 4 button keyboard plugged into the TM1637 board.


Scope photo showing slow rise time of DIO pin (upper trace) on the unmodified TM1637. The lower trace is the CLK. The 8 fast CLK pulses on the left represent the 0x42 command to read keyboard being sent to the TM1637.


Scope photo showing faster rise time of DIO pin (upper trace) with 1000 ohm pull-up on DIO. In both scope photos, the F5 key is pressed; the bits are least significant bit (LSB) first, so read as 10101111 left to right.

The scope photos were taken using the TM1637_keyscan_raw example, with the scope trigger hooked to the TRIGGER pin, and the two channel probes hooked to DIO and CLK. Vertical sensitivity is 2v/division, horizontal timebase is 20usec/division.

Keyscan

Implemented in version 0.3.0 Please read the datasheet to understand the limitations.

//  NOTE: 
//  on the TM1637 boards tested by @wfdudley, keyscan() works well 
//  if you add a 910 ohm or 1 Kohm pull-up resistor from DIO to 3.3v
//  This reduces the rise time of the DIO signal when reading the key info.
//  If one only uses the pull-up inside the microcontroller, 
//  the rise time is too long for the data to be read reliably.

Operation

See examples

Future

Must

  • (0.4.0)
    • remove obsolete init() from code
    • setLeadingZeros(bool on = false) leading zeros flag, set data array to 0.
    • getLeadingZeros()

Should

  • testing other platforms.
  • refactor readme.md

Could

  • keyScan() camelCase ?
  • add debug flag for test without hardware.
    • simulate output to Serial? (HEX)?
  • extend some functions to 6 digit display too?
    • time, celsius, twoint

Wont (unless requested)

  • rotate(bool rot = false)
    • 180 degree rotation of all digits for mounting
    • reverse digit order
    • flip every digit (function to overwrite the char array)
  • HUD(bool hud = false) = Heads Up Display
    • flip every digit
  • investigate if code can be optimized
    • done, => tune setBitDelay()
    • performance measurement
  • displayTest() function ?
    • not needed just print 88888888