Skip to content

Latest commit

 

History

History
55 lines (45 loc) · 2.89 KB

serial protocol.md

File metadata and controls

55 lines (45 loc) · 2.89 KB
Raw

Serial protocol

Pins

Left side of the base PCB:

  • G: GND
  • R: RXD
  • T: TXD
  • Vc: +12V
  • Others: Unused

Settings

115200 Baud, 8N1

Value readback

The device continously outputs it current state.

Example: VAL:D 0 T 248 Vi 11813 Vl 101 Vs 0 I 2500 mWs 0 mAs 0

Each line contains the following fields:

  • Message type marker: Always "VAL:"
  • Device state:
    • 'D': Disabled
    • 'A': Active and in regulation
    • 'U': Out of regulation, i.e. source can't supply enough power. As this load does not measure the current the reported current will be wrong when the load is out of regulation!
  • Error (no column name): Single digit integer (see load.h for error codes)
  • T: Temperature in 0.1°C
  • Vi: Power supply voltage (12V nom.) in mV
  • Vl: Load voltage (screw terminals) in mV
  • Vs: Sense voltage (plugable connector) in mV
  • I: Current in mA. As this load does not measure the current the setpoint is reported.
  • mWs: Energy since start of measurement (in mWs)
  • mAs: Energy since start of measurement (in mAs)

Configuration

Configuration protocol currently is quite simple. There are two command formats:

  • character\r\n: Execute a command without parameters
  • characterINTEGER\r\n: Set a parameter. Integer value must fit in 16 bits

The command is executed when the \n is received. The \r is optional.

Commands:

  • !: Reset UART state. Must be sent after establishing a connection or after receiving an error reply.
  • R: Run
  • S: Stop
  • M: Mode (0=CC, 1=CW, 2=CR, 3=CV, see settings.h)
  • c: Setpoint CC in mA
  • w: Setpoint CW in mW
  • r: Setpoint CR in 0.1 Ohm
  • v: Setpoint CV in mV
  • E: Write settings to EEPROM. Only when settings are changed via the UI they are automatically written to EEPROM. Settings via the serial interface must be written using this command explicitly. However when the user changes any setting via the UI ALL settings are written to EEPROM.
  • e: Read settings from EEPROM. This should be used after controlling the device via the serial interface to restore user's settings.

Once a command is executed the device replies with: CMD:[Received command]. Received command is not necessarily exactly the same string that was sent to the device but the parsed interpretation. For example the response to c01234 is CMD:c1234.

If the command is invalid an error line is produced. Example: ERR:97 0 1 First parameter is the ASCII code of the received command, second parameter is the received parameter and third parameter the error code (defined in uart.h). After each error the interface should be reset. Depending on the type of error (parsing error vs. parameter error) more than one error message might be returned per command. Sending Hello World will probably return one error for each of the characters after the first one as they are all invalid. But don't count on this behavior as the interface might be to slow to output all messages and discard some of them.