![]() RS-232 is more commonly labeled correctly, but of course you have to make sure that the devices are a DTE/DCE pair, or if they're both DTE, there's a "null modem" connection crossing Tx and Rx. ![]() It's uncommon for any two vendors to label their RS-485 conductors the same, so you often have to try flipping them. If you are trying to read a Holding Register instead, you need to select Command 0x03, not Command 0x04.Īlso, the most common serial framing settings are "19200, 8/N/1", meaning 19200 bits per second, 8 data bits, no Parity bit, and one Stop bit.Ĩ/N/1 uses a 10-bit frame (1 Start, 8 Data, 0 Parity, 1 Stop), while 8/N/2 uses an 11-bit frame that is less common.Īnd of course check your wiring. ![]() The most common Modbus RTU command is Read Holding Registers (Command 0x03), not Read Input Registers (Command 0x04), so check to be certain that your meter supports Input Registers.
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