August 2022
Intermediate to advanced
108 pages
2h 23m
English
Content preview from Build a Binary Clock with Elixir and Nerves
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SPI Communication
The next step is to send data to the TM1620 to make it turn on an LED. The flow chart on page 7 of the datasheet shows how to do this:
- Send the command to set the display mode.
- Send the command to write to data memory.
- Send the data bytes describing which LEDs to turn on and off.
- Send the command to turn the LEDs on and set their brightness.
In short, we set the display mode, send a write command, send the data to write, and then send the command to set brightness and go. We’ll take each one of those in turn.
Set the Display Mode
To follow the instructions on the datasheet to set the mode, we need to send 0b00000010, or just the number 2. Click evaluate on the notebook’s Elixir cell that has this code:
| | SPI.transfer(spi, <<0b00000010>>) ... |
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