I am trying to put together a very simple display to read some PID's from my car (no logging, just real-time, chasing a few gremlins and I need more precise info than what gauges on dash can tell me).
I have a UART V1 adapter connected an arduino pro micro w/ atmega 32U4 and 1602 lcd for display.
When I try the sample code "obd_uart_test.ino" or "rpm_led_uart.ino" they both work as they should when the arduino is plugged into my laptop via usb and UART is connected to pro micro's tx/rx.
However, when I try to run the same code w/ just UART adapter, pro micro, and 1602 (no usb connected to computer), it hangs at the obd.begin() command and will not enter main loop.
I thought maybe there is not enough current from UART adapter to power both pro micro and 1602, but that seems to be ok.
I don't think its a power issue. I can get it working with usb plugged in then remove so that arduino and 1602 are drawing power from UART and it works fine.
There seems to be something prohibiting starting communication between UART adapter and pro micro when the usb to laptop is not present.
I can't figure out what the issue might be, any help, direction would be greatly appreciated.