322 Digital Desk Clock
322 : Digital Desk Clock
- Author: Samuel Ellicott
- Description: Simple Digital Clock Project.
- GitHub repository
- Open in 3D viewer
- Clock: 5000000 Hz
- Feedback: ✅ 1
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 serially using an internal 8-bit shift register.
The shift register drives 6-external 74xx596 shift registers to the displays. Clock and control
signals (serial_clk, serial_latch) are also used to shift and latch the data into the external
shift registers respectively. 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.
How to test
Connect serial output to a 6x 8-bit shift registers to display the output on 6x 7-segment displays
External hardware
shift registers, 7-segment displays
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | refclk | serial_data | |
| 1 | use_refclk | serial_latch | |
| 2 | fast_set | serial_clk | |
| 3 | hours_set | ||
| 4 | minutes_set | ||
| 5 | |||
| 6 | |||
| 7 |
User feedback
- sellicott👑: Initial test of design using a logic analyzer connected to the IO pins. an SPI data analyzer was used on (MOSI -> uo[0], CS -> uo[1], SCK -> uo[2]) 8-bit packets were used for analysis (matching the register width of the scan chain output). Other logic analyzer pins were attached to the `refclk` (generated by the rpi pico with the command `tt.pins.ui_in0.pwm(32768)` ), `use_refclk`, `fast_set`, `hours_set`, and `minutes_set`. All pins other than the `refclk` signal were controlled via the commander interface. When no inputs are set the clock runs off the system clock divided to produce correct ticks. The display updates at 1Hz. When the `minutes_set` button is "pressed" the clock enters time-set mode and the clock updates at ~2Hz and the minutes values are updated while the seconds and hours remain constant. Likewise for the `hours_set` button. If both are pressed together then the seconds are reset to zero. Similarly, if `fast_set` was asserted the time is updated at a rate of ~5Hz. When `use_refclk` was selected and an appropriate signal was provided, the clock worked without the need for the system clock divider.