I use this Microchip’s PIC program made in C to control my domotic system for quite some time now, and I think it’s ready to be published.

Below is the readme file, to read the last version, directly go to :

https://github.com/tbarbette/picdomotic

PIC Domotic station

PIC program for a domotic station controlling two temperature sensors, multiple relay, a USB port (for power only) and connected to a PC using UART to receive its instructions.

It uses a PIC18F23K20 but should work on most of them. The PC sends simple commandes through /dev/ttyUSB0 like “A 32” to enable the device 32, or “E 32” to disable it. “T” to get temperature, … See the source code in main.c.

This is MPLAB X IDE project. The only usefull file is in fact main.c, the rest is auto-generated, but I include them if someone would want to directly program the binaries, for example.

Technology used

If you’re looking for sample code, you may find here how to :

Use the UART to communicate with a PC (UART is connected to a “uart usb” module very cheaped that you can find on ebay for example) .
Use the watchdog timer to ensure a device reset if something goes wrong
Use Brown-out to jump to do an interrupt and do “something” (blink in my case) if the voltage goes below some threshold
Use the ADC to read the temperature given by two LM35
Read/write to eeprom
Control a 5V relay board with a 3.3V relay board using NPN Transistors (when I’ll add the schematic though)

The python script used to manage the PIC controller is available athttps://github.com/tbarbette/monitoring/blob/master/scripts/relay.py and a small HTTP server allowing you to remotely control it is available athttps://github.com/tbarbette/monitoring/blob/master/scripts/server.py

More a little post-it than a post, I wanted to put somewhere the commands :

Using the eeprom is as simple as these two commands :

[code lang=”c”]EEPROM_READ(addr)
EEPROM_WRITE(addr,value)
[/code]

A little example (reading from the USART a value and putting it in the EEPROM address 0x00)

[code]
while (!DataRdyUSART());
char data = ReadUSART();
EEPROM_WRITE(0x00,data);
[/code]

Note that theses header are defined in the standard xc8 header which will include (or , …) or High Tech C headers if you come from the past :

[code lang=”c”]
// MACROS for EEPROM Access
/* macro versions of EEPROM read and write */

/* NOTE WELL:
EEPROM_READ() is NOT safe to use immediately after any
write to EEPROM, as it does NOT wait for WR to clear. This is by
design, to allow minimal code size if a sequence of reads is
desired. To guarantee uncorrupted writes insert
while(WR)continue;
before calling EEPROM_READ().
*/

#if _EEPROMSIZE > 0 && defined(_PLIB)
#define EEPROM_READ(addr) Read_b_eep(addr)
#define eeprom_read(addr) Read_b_eep(addr)
#else
#define EEPROM_READ(addr) 0 // Added only for code portability
#define eeprom_read(addr) 0
#endif

#if _EEPROMSIZE > 0 && defined(_PLIB)
#define EEPROM_WRITE(addr, value) (Busy_eep(), Write_b_eep(addr,value))
#define eeprom_write(addr, value) (Busy_eep(), Write_b_eep(addr,value))
#else
#define EEPROM_WRITE(addr, value) // Added only for code portability
#define eeprom_write(addr, value)
#endif
[/code]

Category: Electronic