ftjuh/servocontroller

Control up to 10 servo motors via I2C with this firmware for ATtiny2313 and ATtiny26 originally by Stefan Frings

servocontroller's Issues

ESP8266 controller will crash the target firmware if addresses >=0x40 are used on the bus

ESP8266 as controller uses a very tight timing after a start condition. Analysis with a logic analyzer shows that the ESP8266 will pull SDA up very soon after pulling SCL low. Addresses >= 0x40 will result in a '1' bit sent immediately after that.

Logic Analyzer output from Pulseview (remove ".zip" from file extension): 0x40 24Mhz 20k samples.sr.zip

The original code will erroneously interpret this as a stop condition because it does not buffer the state of SDA between detecting a pin change and interpreting this change as a stop condition. Also, it ignores SCL in doing so.

        // Wait until end of start condition or begin of stop condition 
        while ((PINB & 128) && !(PINB & 32));

        // Break when a stop condition has been received while waiting
        if (PINB & 32) {
          break;
        }

After the false detection of a stop detection the above break; command will cause an exit from the main loop, putting the device in an undefined, non reactive state.