[PIC] LCD data show garbage

[Manjuhb]

Recently I develop one project in which total 5 DC motor. The project contain 16x2 LCD display with PIC16F886. When use press key then motor will run. I observe that after some key operation LCD show garbage & it remain few minute. LCD runs in 4 bit mode. Garbage comes randomly some times for 3 iterations some times for 10 iterations and this design is done on the PCB board. Please let me know what could be the problem.


I have 0.1uF cap across the PIC IS also.
To drive motor I have used L298n H-bridge IC. I have used flywheeling diodes also across the motor connection.

 

[KlausST]

Hi,

most probably EMC problems.

caused by:
* wiring (maybe dividing power wires from signal wires, or the use of drilled pair wiring or shielded cables...helps)
* PCB layout (GND_plane, GND_plane, GND_plane!... EMC filters, low impedance signal lines...capacitors, a ceramics at least on each VCC pin, bulk capacitors, and on signal lines like RST)
* I/O EMC filters, I/O ESD protection
* system clock circuit..

Klaus

 

[andre_luis]

Feeding the microcontroller by the same power bus alread used by log devices is always a potential risk issue. In general it is a good choice to separate both.

 

[Manjuhb]

Feeding the microcontroller by the same power bus alread used by log devices is always a potential risk issue. In general it is a good choice to separate both.

We have all ready done 50 board. Please let me know how to solve this problem in existing boards. Thanks

 

[Easyrider83]

May be you should show us that boards first?
Btw, schematics also will be helpfull.

 

[Manjuhb]

Please find the attached schematics

 

[Easyrider83]

And pcb, please. Schematic looks good. Unused pins of LCD I recommend you to connect to ground.