Need help with starting my car

Need Help With My Project
1

Hello

I have ttgo t-call sim800L connected to blynk via GSM and I am using 8relay shield with MCP23017 with lastest iOS

My question is how to handle starter of car…

unsigned long startMillis = millis();
unsigned long currentMillis = millis();
while ((rpm < 650) && (currentMillis - startMillis < 2000)) {
        mcp.digitalWrite(startRelayPin, false);
        currentMillis = millis();
        Blynk.run();
}
mcp.digitalWrite(startRelayPin, true);

rpm sensor is connected via interupt pin and calculates rpm from frequency. sorry for my english and stupid question but I’m noob :slight_smile: i can publish whole code but it has over 700lines

2

What exactly is your question?

Pete.

3

my question is how to make it differently… because while starting blynk isnt responding and sometimes it starts longer than it had…

4

To avoid killing your starter just because the Blynk MCU locks up… perhaps separate your starter relay and RPM sensor into its own non-Blynk code on dedicated MCU that can than interface with the Blynk MCU as needed (via i2c or even serial perhaps?) EG. to start when asked, sense results, abort/retry as needed and confirm success back to Blynk MCU when finished.

5

what type of MCU should I use? can you recomend me something? relays are connected to MCP23017 via i2c, (sometimes not working as I expect… maybe my fault :smiley: )

6

You should either use a NodeMCU/Wemos D1 Mini, or an ESP32. If you went for the ESP32 then you’d have many more useable GPIOs so you probably wouldn’t need the MCP23017.

Pete.

7

problem of using ESP32 pins is that while boot or restart some pins have some output… and while restart or something unexpectable relays cannot change states, and I have lot of inputs like: ( RPM , lockStatus, keyIn, oilPressure, battery ) all this is connected directly to ESP32 allso i have temperature sensors, LDR sensor, and currently using 8 relay and wanted more :rofl: … maybe im not using the right HW but i am not an electrician

8

Yes, but if you take a look at this, you’ll see that there are many ESP32 pins that are suitable for use with relays:

But of course there’s nothing to stop you using an ESP32 and one of more MCP23017s.
I did a few experiments with MCP23017s recently and wrote-up some of my findings here:

Pete.

9

Also, have you thought about using CANBUS to do this?
The ESP32 has a CANBUS interface and if your car has OBDII then it ‘should’ be possible.

Pete.