nmea0183
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| nmea0183 [2025/03/18 18:16] – created river | nmea0183 [2025/03/21 23:11] (current) – river | ||
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| RS 422/RS485 levels should be at least +/-200mV to register as 1 or 0. Nominal drive 5V. | RS 422/RS485 levels should be at least +/-200mV to register as 1 or 0. Nominal drive 5V. | ||
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| + | Idles high, same as RS232 and UART. | ||
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| + | ===== RS422 (and 232) adapter tests ===== | ||
| In practice I have seen (open circuit unless otherwise stated): | In practice I have seen (open circuit unless otherwise stated): | ||
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| * Cheap iMac colour USB -> 485 dongle: +500mV, -3.5V. | * Cheap iMac colour USB -> 485 dongle: +500mV, -3.5V. | ||
| * Cheap UART to RS422 board, with chip marked MAX490: +/- 4.3V open circuit, dropping to -4.1V, +1.2V when connected to XB8000 receiver. | * Cheap UART to RS422 board, with chip marked MAX490: +/- 4.3V open circuit, dropping to -4.1V, +1.2V when connected to XB8000 receiver. | ||
| + | * Combined RS232/RS485 USB adapter: 483: +0.3V,-3V, 232: +/-9V. | ||
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| + | I think the ones that only go up to +0.3V or so are not actually engaging the driver except on the 0 bits, so this value is just failsafe pullups giving (barely) a 1. I have checked this by measuring the DE pin on the combo 232/485 adapter. | ||
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| + | I tried to get it to enable the driver by setting DTR and RTS in a python script but it didn't work. | ||
nmea0183.1742321773.txt.gz · Last modified: 2025/03/18 18:16 by river