Solution to "I2S video output and wifi lead to a reset"

[Martin-Laclaustra]

Dear Matthias,
thank you for your work on this project.
You posted here a question to Jan: "Unfortunately using I2S video output and wifi at the same time lead to a reset after few seconds. Do you have an idea, how to fix that?"
This is the solution:
This line:

esp8266-ntsc-c64-emulator/ESP8266-NTSC-C64/generate_video.c

Line 65 in 91f3519

LOCAL void slc_isr(void) {

should be changed to:
LOCAL void ICACHE_RAM_ATTR slc_isr(void) {

and this one:

esp8266-ntsc-c64-emulator/ESP8266-NTSC-C64/cpu.c

Line 1104 in 91f3519

uint8_t read6502(uint16_t address) {

should be changed to:
uint8_t ICACHE_RAM_ATTR read6502(uint16_t address) {

The latter change could be more elegantly solved, keeping functional parts separated. Instead of directly using read6502 within slc_isr, I suggest to copy the relevant memory values (with read6502) to a global array or struct (3 elements) in the main loop. Then just read directly the array in slc_isr. After that change, adding ICACHE_RAM_ATTR to read6502 will not be needed anymore.

I confirm that with the ICACHE_RAM_ATTR edits above (and changing the relevant parts to always start ArduinoOTA, of course), I can reflash while video is on (video stops on reflashing and resumes after the automatic reset).

I have several ideas about structuring the code to make development easier that I will try to share; most are about separating 6502 emulation, memory mapping (should we say "masking"?), (partial) VIC II simulation, video output (NTSC, PAL, color), and user interaction (keyboard input vs telnet vs webpage).

Thanks again.