From: bjornhk@dhhalden.no (BJORN HAAVARD KLEVEN) Subject: GUS MIDI connector Date: Sun, 10 Jan 1993 23:13:12 GMT The MIDI connector box for the GUS will not be out for a while, the work with it at Gravis isn't proceeding too fast. However, a relatively easy and inexpensive way - that works - is to use an SB connector kit and replace the 6N136 chip with a 6N138 or -139. In addition, add a 5.6K ohm ressistor between pin 5 and 7 on the chip, and one between pin 6 and 8. This definitively works, I'm using one myself! Happy soldering, -=* Bjorn :: bjornhk@sofus.dhhalden.no ACCESS DATA :: TEL: (+47)-9-17 50 48/61-97 311 FAX: 61-97 312 BBS: 61-97 304/97 94 945 ----------------------------------------------------------------------------- From: remek@mamura.ee.mu.oz.au (Remek Lipinski) Subject: GUS: Working MIDI connection circuit. Date: Sun, 10 Jan 1993 10:35:47 GMT I have used the following circuit to connect to the Ultrasound to get the MIDI port working. This has been posted before but to get it to work I had to change one of the resistors, namely the pullup resistor connected between pins 6 and 8 of the optoisolator I also used 6N138 insted of 6N135 (I couldn't get it at the time). Also the inverters have to be able to work at a high speed (i think midi is around 19000 but I am not sure), one of the inverter chips I used didn't work even though the chip was fine, I guess it could not handle the speed. I then tested the port by playing something on the keyboard and listening back to the seqence, the timing seemed ok. to make sure I installed a Roland MPU 401 card into the pc and connected its midi out to the midi in of the Gravis. I then used one sequencer to play something out of the Roland port and another sequencer to record with the Gravis port. Then I listened to the recorded sequence by playing it first through the Gravis midi out and the through the Roland midi out, both sounded exacly like the original. Anyway I hope this will be useful to someone, I for one am happy to have the Gravis midi port working (for the fraction of the cost of what the SB connector box costs). 15 pin D connector 220R pin-1 +5v ----+--------------------------/\/\/\---------------\ | \ 4 | Gnd--2 MIDI OUT | |\ |\ 220R / 5 pin-12 tr >---|------| o-----| o----------/\/\/\--------------/ | 14|/ 13 12|/ 10 | 220R +---------------------------/\/\/\-------------\ | \ 4 pin-15 rx <---|--------------------+ Gnd--2 MIDI THRU | |\ |\ | 220R / 5 | +--| o-----| o---+-------/\/\/\------------/ | | 1|/ 2 3|/ 4 | | | +------+ | 270R* | 220R +--/\/\/\--+ +------+----------/\/\/\--------\ |B |C |A | \ 4 +-|----------|----|-+ | MIDI IN | 8 6 2 | ----- / 5 | | / \ IN914 or IN4148 +-/ | 6N138** | --- | | | | | | 5 3 | | | +------------|----|-+ | | | |K | | pin-5 Gnd --------------+ +------+----------------------+ Inverters are LS7404 Leave pin 2 of the MIDI IN unconnected (Don't connect to ground) * this resistor was 5.6K in the original post, I used a the 6N138 optoisolator and found that this value was too high as not enough current was allowed to sink into the collector of the output transistor. **In the original post this was 6N135, I could not readily find this here (Australia) so I used 6N138 which I think is funcionally the same, one of the catalogues stated that this is a "high speed MIDI standard" device. Happy GUSing. =============================================================================== ** Remek Lipinski : remek@mullian.ee.mu.OZ.AU ** ** "I'll be back!" - T800 ** =============================================================================== From ral@mlb.dmt.csiro.au Tue Jun 14 09:18:44 1994 Date: Tue, 14 Jun 94 09:27:00 +1000 From: Remek Andrew Lipinski To: lippman@honeydew.cc.wwu.edu Subject: Re: Question about MIDI Box for GUS Yes the Vcc and ground pins on all IC's have to be connected to +5v and 0v respectively. The correct mapping for the 5 pin connector, looking at the front of a socket, are: --- / 2 \ | 4 5 | | 1 3 | \__^__/ Let me know if you need any more help. Remek.