I am attempting to mimic a midi driver that uses a TI LS05 hex inverter to drive a wireless transmitter for a midi data stream from a digital accordion controller to the off-board module (commercial brand is Millennium, Version 4.0). It is my goal to convert a Version 3.X Millennium to become wireless.
I am having difficulty to select the correct hex inverter. I don't know much about TTL design. I first used an NTE777 hex inverter from Fry's. The wireless system drops some of the pulses in the midi/UART data stream. Then i built a circuit with a SN7416 open collector. It still drops pulses from the stream (observed with a DSO). It appears that my driver does not provide a good high level to the wireless, which then fails to "see" some of the pulses. The circuit is the same. The components are different, i.e. primarily the hex inverter. My driver output reaches only 4.0 V for the high level, whereas the LS05 in the Version 4 provides a full 5.0 volts. I strongly suspect this is the problem.
I am having trouble finding an LS05 in small quantity. Many variations. Samples available are for surface mount (which is the original design), not for my breadboard. And, for that matter, not sure which LS05 to use....there are several. Can someone give me some guidance or recommend which equivalent hex inverter chip to use to mimic the LS05 from TI? Or, can I pull up the output of the second inverter with a resistor (there is no pullup on the output in either design)?
Added information: When I bypass the wireless system and hardwire my prototype driver in the Version 3 directly to the accordions off-board module, it works fine. It is the wireless system that drops pulses. Of course, in the hard wired case, there is no transmitter in the loop and the level requirements are different. It is the wireless transmitter that doesn't pass along the pulses when the high level is only 4 V. But the same transmitter works fine in the Version 4.0 controller where the driver provides 5.0 volt high levels. Los levels are identical in both cases.
I am having difficulty to select the correct hex inverter. I don't know much about TTL design. I first used an NTE777 hex inverter from Fry's. The wireless system drops some of the pulses in the midi/UART data stream. Then i built a circuit with a SN7416 open collector. It still drops pulses from the stream (observed with a DSO). It appears that my driver does not provide a good high level to the wireless, which then fails to "see" some of the pulses. The circuit is the same. The components are different, i.e. primarily the hex inverter. My driver output reaches only 4.0 V for the high level, whereas the LS05 in the Version 4 provides a full 5.0 volts. I strongly suspect this is the problem.
I am having trouble finding an LS05 in small quantity. Many variations. Samples available are for surface mount (which is the original design), not for my breadboard. And, for that matter, not sure which LS05 to use....there are several. Can someone give me some guidance or recommend which equivalent hex inverter chip to use to mimic the LS05 from TI? Or, can I pull up the output of the second inverter with a resistor (there is no pullup on the output in either design)?
Added information: When I bypass the wireless system and hardwire my prototype driver in the Version 3 directly to the accordions off-board module, it works fine. It is the wireless system that drops pulses. Of course, in the hard wired case, there is no transmitter in the loop and the level requirements are different. It is the wireless transmitter that doesn't pass along the pulses when the high level is only 4 V. But the same transmitter works fine in the Version 4.0 controller where the driver provides 5.0 volt high levels. Los levels are identical in both cases.