Hyuduo LED 7 Segment Display, MODBUS-RTU Display Module, 4 Digits Display with RS485 Serial Port for PLC Communication (5-36V)

worked great

Excelente display, muy buen brillo y tiempo de respuesta. Compré 3 y los usamos directamente en una red modbus rtu con controladores s7-1200 y funcionan correctamente. Configuración sencilla y rápida. Compra recomendada

No documentation. imposible to set it up.

The functionality and price of this product are excellent. Unfortunately, as others have noted, it is very difficult to find any technical information (e.g., no manual, no customer support, etc.). Thanks to other reviews here and elsewhere I was able to piece together enough information to use it (e.g., default node/slave ID is 1, baud rate is 9600, write to holding register 0 to set the number 0-9999 to be displayed). However, the information was not complete or entirely correct, so I am adding my notes also: * Register mapping: 0: number to be displayed: values 0-9999 map to 0000 to 9999, as expected. -1 to -999 can be displayed as well (2's complement, e.g., 64537 = -999). For positive values there are leading zeros, for negative ones the minus sign appears on the left then blanks are padded until the first non-zero digit. While I didn't find a proper way to disable leading zeros, I did notice that sending 20000 to 20999 displays _000 to _999 (one leading zero suppressed, though I suspect it is a glitch / accident / coincidence. 1: Decimal point position (0 for none, 1 for XXX.X, ... did not test much) -- stored [persists after power loss] 2: Brightness -- stored [persists after power loss] 3-5: unknown function 6: Setting to 0 causes blinking; setting 256 causes steady (non-blinking) illumination stored [persists after power loss] 7: Baud rate 0-7 (1200, ..., 115200) 8: Slave/Node ID 0-255 (did not try setting the high byte in the register to anything other than 0) 9-255: unknown * Registers appear to "wrap around" after 255, e.g., setting "register 256" is equivalent to setting "register 0" * When the device is first powered-on it will display its node/slave ID using the first (left-most) digits and its baud rate code using the last (right-most) digit. e.g., 2557 means node 255/0xFF using baud rate code 7 for 115200 bps. * Device uses STC8G1K08 microcontroller and TM1650 segment driver

Item arrived with no documentation whatsoever. Product listing has insufficient information. back it goes.