Compiled with SDCC (last used 4.0.2 #11679 (Linux) ) http://sdcc.sourceforge.net/ . Programmed with easy-pdk-programmer (1.2) https://github.com/free-pdk .

PDK8574 - I2C GPIO expander, similar to PCF8574

i2c-SFRaccess - created to ease development and debugging pdk uc's with it you can set/read internal registers through i2c and test values without wasting OTP ic's

i2c-fancontroller - WIP - i2c controller for PC FAN (with 4pins) currently it can: set fan speed trough pwm duty cycle, read speed in hertz and RPM. It contains some tips how to read/write t16 counter, use comparator as additional pin change interrupt

i2c-slave-minL1(L2) - some bare minimum i2c slave implementation

WARNING: all that code depends on SDCC peephole optimization. It's pattern search&replace on asm code. I have wrote some rules to meet timing requirements of i2c communication, they are in peephole_rules folder

Edit Makefile in selected project, adjust sdcc and easypdkprog path use make to compile and, make flash-PFS154 to flash it