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Department of Microelectronic Systems, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology

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Driving LED display using Picoblaze processor

Introduction

The main goal of this exercise is to develop a microelectronic system with the processor Picoblaze, where the clock division and LED display multiplexing is done in hardware. Reading buttons, increasing and decreasing the displayed values are done by software.
To check the functionality, the sub-block has to be embedded in a circuit enabling setting (with switches and buttons) and displaying on LED display of Spartan 3 board any hex number with decimal points.

Proposed block diagram
Fig. 1. The proposed block structure. The sub-block ports that should be used in the project are indicated in the block diagram. The connections between blocks are not shown.

Operation scheme

Display should show "0000" after reset.
For simplicity, only one LSB digit (out of four) can be changed, displayed in hex format.
Pressing BTN0 should increase the displayed value by 1, e.g. "0000" "0001".
Pressing BTN1 should decrease the displayed value by 1, e.g. "000a" "0009".
After overflow the counter should start from 0, e.g. "000f" + 1 "0000", "0000" - 1 "000f".
Basic debouncing should be applied in the project. The button release should be controlled.
Picoblaze's clock should be 1 kHz.
Reset can be connected to the switch SW7.
Picoblaze has synchronous reset port - reset occurs when reset pin is high and at the rising edge of the clock clk.

Possibilities of enhancements (for volunteers)

Setting all the digits instead of only one (selection of the edited digit can be done using buttons BTN3 and BTN2).
Edit Mode and Display Mode: the display only shows the entered value (Display Mode). After pressing and holding the button BTN3 for more than 0.5 sec, Edit Mode is activated. Currently edited digit should blink. Quitting the Edit Mode - after pressing and holding BTN3

Constraint file ucf, Digilent Spartan-3 board, Spartan-3 3S200 FT256-4:
#########################################################################################
# Clock:
NET "clk_i" LOC = "T9" ; # 50 MHz clock
#########################################################################################
# Reset:
NET "rst_i" LOC = "K13" ; # BTN0 active high
#########################################################################################
NET "led7_an_o<3>" LOC = "E13" ; # leftmost digit, active low
NET "led7_an_o<2>" LOC = "F14" ; # active low
NET "led7_an_o<1>" LOC = "G14" ; # active low
NET "led7_an_o<0>" LOC = "d14" ; # rightmost digit, active low
#
NET "led7_seg_o<7>" LOC = "E14" ; # segment 'a', active low
NET "led7_seg_o<6>" LOC = "G13" ; # segment 'b', active low
NET "led7_seg_o<5>" LOC = "N15" ; # segment 'c', active low
NET "led7_seg_o<4>" LOC = "P15" ; # segment 'd', active low
NET "led7_seg_o<3>" LOC = "R16" ; # segment 'e', active low
NET "led7_seg_o<2>" LOC = "F13" ; # segment 'f', active low
NET "led7_seg_o<1>" LOC = "N16" ; # segment 'g', active low
NET "led7_seg_o<0>" LOC = "P16" ; # segment 'dp', active low
#########################################################################################

#########################################################################################
# Push-buttons:
NET "button_i<3>" LOC = "L14" ; # BTN3 active high
NET "button_i<2>" LOC = "L13" ; # BTN2 active high
NET "button_i<1>" LOC = "M14" ; # BTN1 active high
NET "button_i<0>" LOC = "M13" ; # BTN0 active high
#########################################################################################

Additional information

Skrócony opis procesora picoblaze