Debugging digital Scales for a DRO

Hopefully, the scales connected to the DRO:int4 work without hunting for errors. If the automatic setup detected all scales connected, there is no need to read on.

Should you have an oscilloscope (a 1 channel 20MHz scope is by far enough) the part describing the protocols has a lot of scope screens printed. They might be more helpful for a first look.

Chapters:

• Common Errors
• Debugging with DRO:int4

Common Errors

The most common error is that the wires were connected wrong. If the scale is connected to the DRO:int4 and power is on the DRO:int4, the scale should show some digits in it's display and react as expected (zero, move slide, change unit etc.). If it does not, check the polarity directly at the scale. A voltmeter (no special requirements) is helpful.

Description:

• Pin 1: neg. voltage
• Pin 2: data
• Pin 3: clock
• Pin 4: positive voltage

The voltage between pin1 and pin4 should be 1.55V (+/- 0.5V) with the positive on pin 4.
If the voltage is reverse, quickly disconnect the scale and shorten the pins 1 and 4 with some wire (or pliers) for some seconds. Let it rest for at least 1 hour (yes, this is voodoo). Resolder properly and try again. Chances are, that the scale is not ruined. Mine survived this procedure 2 times.

Debugging with DRO:int4:

DRO:int4 has an automatic scale detection that also helps in finding errors. To have access to this feature, a terminal-program is necessary. Any terminal-program that is configured with these parameters works:

• 19200 Baud
• 8 Bit
• 1 Stop Bit
• No parity
• No XON/XOFF, nor RTS/CTS

Here is a terminal program with all the parameters readily configured (term.exe).

Connect the PC -with the terminal-program running- to the DRO:int4. Power up the DRO:int4. There should be a message coming that reads like this:

*** Welcome to YADRO-land! ***
(c) 2005 Nick Mueller // www.yadro.de

The next step is to find out what scale is making problems. This is done by typing the command "d0" at the terminal-program's console (no <Return> at the end). There might be 3 possible messages:

Checking device #0...
Clock : Signal
Data  : Signal
Device: 7BCDs ('B')

This message shows, that there is no problem with that scale and that it is one of the (rare) that sends 7 BCDs.

An other possible (and positive) answer is:

Checking device #0...
Clock : Signal
Data  : Signal
Device: 2*24bits ('L')

This is also a detected and OK scale. It is of the type that sends two times 24 bits.

Possible answers of undetected scales are:

Checking device #0...
Clock :stuck H
Data  :stuck H

Checking device #0...
Clock : Signal
Data  : Signal
Device: unknown type. Sending 0xnn

… then chances are very high, that clock and data is flipped. That there is a signal means, that there is some signal. But this signal is not detected by the firmware of the uC. The number behind "Sending" shows the number of bits received (in HEX).

Proceed with the other scales, by sending the command "d1", "d2" or "d3" (depending on what channels scales are connected to).