546 Digital Desk Clock v2.0
546 : Digital Desk Clock v2.0
- Author: Sam Ellicott
- Description: 7-Segment Digital Desk Clock for ihp Tapeout
- GitHub repository
- Clock: 5000000 Hz
How it works
Simple digital clock, displays hours, minutes, and seconds in either a 24h format.
Since there are not enough output pins to directly drive a 6x
7-segment displays, the data is shifted out over SPI to a MAX7219 in 7-segment mode.
The time can be set using the hours_set and minutes_set inputs.
If set_fast is high, then the the hours or minutes will be incremented at a rate of 5Hz,
otherwise it will be set at a rate of 2Hz. Note that when setting either the minutes, rolling-over
will not affect the hours setting. If both hours_set and minutes_set are presssed at the same time
the seconds will be cleared to zero.
A block diagram of the system is shown below.
How to test
Apply a 5MHz clock to the clock pin and 32.786Khz signal to the refclk pin.
Use the hours_set and minutes_set pins to set the time.
External hardware
Connect the BIDIR PMOD to a MAX7219 7-segment display, For reference Tiny Tapeout SPI
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | refclk | Display CS | |
| 1 | Display MOSI | ||
| 2 | Fast/Slow Set | ||
| 3 | Set Hours | Display SCK | |
| 4 | Set Minutes | ||
| 5 | |||
| 6 | |||
| 7 |