![]() ![]() The levels used are far from standard-compliant, but the USB-to-UART converter accepts it. In my case adding a resistor of 10k between the negative output of the charge-pump of the level shifter of the USB-to_UART converter, and the RxD pin fixed this. I am using a USB-to-UART converter which did not include a pull-down on RxD to pull the input to idle level when nothing was connected. This might have worked on old-fashion implementations of a serial port, but in my case it did not. The implementation of TxD only uses a pull-down between signal ground and the TxD pin using the transistor of the opto-coupler and a 3.3k resistor. The schematic of a MS-9150 shows that only TxD and RxD are connected, and that opto-couplers are used for isolation. This is caused by the implementation of the TxD 'transceiver' of the MS-9150. Both RxD and TxD lights were showing activity, the TxD light however was only very faint. Using this adapter the connection seemed correct, but I did not see a response on my screen yet. Finally a DB25F-DB9M converter and a DB9F-DB9F gender changer made the proper connections for TxD and RxD (These came from my stock, I guess a DB25F to DB9F should work as well). (Commands are executed after sending a linefeed ' n' character) To get the device connected to my PC a breakout box with lights to check the connections turned out to be very useful. The port on this device is RS-232, using following settings: Baudrate 1200 Databits 7 Stopbits 2 Parity None Handshake None Protocol: D: return the value measured. In the end I got it working so I thought I would share my findings. ![]() The posts here got me started on the RS-232 connection of the device. This appears to be the same device as a Metex MS-9150. Hello, Some time ago I became the owner of a Tenma 72-5085. In the early days of USB adaptors, they did NOT work with all hardware, and a true serial port was necessary. It was always easier if you used a propriety package, though the name of the one I used eludes me. Comm1, comm2, comm3 or comm4 were the only choices if I remember correctly, but usually Comm1 or Comm2. You needed to use a Baud rate that was not too fast for the particular device, and select which com port. I have never used Windows, but used to use DOS, 20 years ago. I seem to recall it is a null-modem cable. ![]()
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