Hi there Midi folks I,m just half way throught my first midibox and have got stuck on getting the midi in to work. Have run throught the fault finding and have come up with the following results.The problem i have is i,m a bit confused to what the problem is. * Check the resistor values at the MIDI In Port: R11=220 Ohm (resistor code: red-red-brown), R6=1.2kOhm (brown-red-red), R5=5.6kOhm (Green-Blue-Red). ok * solder two cables to the bottom side of the core module like shown in mbhp_core_midiin_debug.gif. The LED should lit (take the polarity of the LED into account, the short leg is the cathode and has to be connected via a resistor to Vss). So long as single MIDI events are received, you won't notice a difference, but with a continuous SysEx stream the LED should begin to flicker. Note:so long as the LED is connected directly to the Rx pin, the PIC will *not* receive the MIDI data due to the power consumption of the LED. This method is only usefull to test if the MIDI signal is available at the Rx pin FAIL * if the LED doesn't lit, connect the anode to the optocoupler (Pin IC2:6). FAIL If it still doesn't lit, connect the anode with the +5V rail of the optocoupler (Pin IC2:8 ) PASS * If this doesn't help you to detect the error, continue with the next step - see mbhp_core_midiin_debug2.gif - in this configuration the LED should only lit when MIDI data is received. Than more MIDI events are received a time, than brigther the LED. If the LED doesn't lit, check the polarity of the protection diode D1 before the optocoupler (again...). Also check the polarity of the MIDI cable (again...).PASS * Standalone test for the optocoupler: mbhp_core_extract_opto_test.gif PASS * A second standalone test for the optocoupler, this time the optocoupler isn't plugged in the core module: mbhp_core_opto_test.gif NOT DONE * final check to ensure that all 4 MIDI ports are working: put the PIC out of the socket and loopback the MIDI IO ports at the Rx/Tx pins like demonstrated in mbhp_core_extract_io_loopback.gif. Send any SysEx dump by using the "Send/Receive SysEx" function of MIDI-Ox. The number of sent bytes must match with the number of received bytes. FAIL Thanks in advance