If you connect the YADRO-interface to your PC, start a terminal program (having set up the baud-rate properly) and then power up the YADRO-interface, you will be welcomed by:

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

I have assembled a very simple terminal program (TERM.EXE) for you that connects to COM1 and sets the baud rate to 19200Bd. Nothing valuable, but it works under DOS. You can change the default-port (COM1) by invoking Y-TERM with -c:COMx (x being the port#).
You don't have to terminate commands with a CR or so.

YADRO's RS232 characteristics:

• 19200 baud
• 8 bit
• 1 stop bit
• no handshake (neither XON/XOFF, nor RTS/CTS)

Note, that commands are case-sensitive! All responses from the controller are terminated by a CR/LF

command (Typed in a the console)	action (happening inside the controller)	response (from the controller)
v	version Displays version of firmware	YADRO-DROINT v0.2c
d0 d1 d2 d3	Debug/display device #0… device #3 verbose information. Valid range is 0..3. If you are out of range, you'll get a warning. A "d"-command prepares the interface for reading from a (connected) device. If you start the YADRO for the very first time, you need to do at least a "da" or a "d0" etc. for each digital scale connected. If you don't do that, you will get error-warnings when trying to read from that port. This command may take up to 2 seconds. It will even take longer if you connect some low frequency generating device to it. But you don't.	If nothing is connected to the port: Checking device #0... Clock :stuck H Data :stuck H If something is connected: Checking device #0... Clock : Signal Data : Signal If that something is recognized: Checking device #0... Clock : Signal Data : Signal Device: 7BCDs ('B') or Checking device #0... Clock : Signal Data : Signal Device: 2*24bits ('L')
da	Does a "d0", "d1", "d2", "d3" for your convenience in one block.	see d0…d3
dw	Writes the information gathered by a "da" or "d0"…"d3" command into the interfaces non volatile memory (EEPROM). If you switch off and back on again, that information is read back automatically, so you don't have to go through a "da" sequence every time you power the YADRO-interface up.	OK
dr	dr is the inverse of dw. It reads the configuration from the EEPROM. You normally don't need that command, as YADRO reads that information after each reset/power up. But it helped me to find a nasty bug. So I'll leave it in there. The numbers you get are 8bit hex and representing the number of bits the scale connected to the ports (from left to right / from dev0 to dev3) is reading. 00 means nothing connected. A 31 would be a type "L" scale.	31313100 OK
r0 r1 r2 r3	Read from device #0…#3. You have to have set up the interface at least once with a "da" command. The output is in hex, terminated with a CR. The bit order is exactly the same as it was received. There is no interpretation at all. After the device#, there is a character indicating the type of device connected. It is either a "B" or a "L"	DRO#0B:0x00112233 or DRO#0L:0x0011223344
s0 s1 s2 s3	Sample device 10 times. This is a burst read from one device. E.g. like calling 10 times the "r" command very fast. You can use this to find out (during setting up) whether your digital scale can be switched to fast mode. It also might help in averaging the reading of that port on the PC side.	10 times like a r0, r1, r2, r3
a	Active mode. In this mode, all ports are read in an infinite loop and, whenever a port changes it's value, it is sent. When no reading changes, no data is sent at all	OK Then: see r0, r1, r2, r3
p	Passive mode. Just terminates the active mode. The passive mode (or "polling mode") is the mode when the YADRO is powered up. To get readings in that mode, you have to ask (to poll) values with "r0"…"r3" or with "s0"…"s3"	OK
c0C c1C c2C c3C	Config port, by pulling Clock high. This command pulls the Clock line of the digital scale to high (1.55V) for 1 second. It helps in switching modes. See the previous pages and the description for details. Note that the second "C" is capital.	OK
c0D c1D c2D c3D	Config port, by pulling Data high. This command pulls the Data line of the digital scale to high (1.55V) for 1 second. It helps in switching modes. See the previous pages and the description for details. Note that the "D" is capital!	OK
R	Resets the interface. This is a software-reset, and the command might be quite useless. But it exists.	The welcome text

Be friendly to your interface! Do not flood with commands, but wait 'till you get a response. If you do send a command before you got a response, the command will simply be lost. The controller only buffers one complete command and empties that buffer after the command is processed. If you send unrecognized commands, they will simply be purged without any comment.

Schematics

For reference, here is the schematic of the DRO:int4. Sorry for the bad quality of the PDF.

Publishing the schematic does not mean that it is freeware. (C) is still by me and any commercial usage prohibited!

BOM

Part#	Spec.	Comment
Capacitors
C1…C5, C10, C12, C13, C15	100n	ceramic
C8, C9	22p	ceramic
C6	10u	electrolytic, 6.3V
C11, C16	1000u	electrolytic, 33V
C7	22u	electrolytic, 6.3V
C14	1u	tantalum, 6.3V
not drawn	1u	tantalum, 2V min., going in each digital scale
Resistors
R1, R2, R5…R12	100	R1, R2 metal film, 1%
R3	56	metal film, 1%
R4	220	metal film, 1%
R14, R15, R23	330
R16, R19..R22	3k9
R13, R17, R18	10k
Diodes
B1	B40C800	bridge rectifier; minimum 20Volts, 200mA;
LED1	--	power on LED; high eff type
Integrated Circuits
IC1	MAX232N (TI) or MAX232ACPE (Maxim)
IC2	LM317LZ	TO92 case
IC3, IC4	LM2901N
IC5	CD4051N (DIL case)	can be 4051B to
IC6	Atmel ATtiny2313-20PI	a Atmel 90S2313 does not work
IC7	uA78S05	1.5 Amps (200mA would be enough)
OK1, OK2	HCPL4502 or 6N136
Misc
Q1	20MHz (HC18 case)	can be the higher case to
DC1	5V/5V DC/DC	5v-5v DC/DC converter; isolated; 1W; output unregulated +/-10% SIL4-case. They are all called "xxx0505S".
J1	MTA02-100	Molex
J2	MTA03-100	Molex
X2	9 pin D-sub male	get a PCB mounting or a front mounting one
SV2…SV5	6 pin header	pin 6 is NC
SV1	10 pin DIL-header, male	might be left out depending on your programming means.
not drawn	power supply 7 …9 V AC, 200mA min.
not drawn	null-modem cable 9 pin female/female	length as required

All Rs are 1/4Watt, 10%. Except R1, R2, R3 and R4 that should be 1% metal film.
Voltages of electrolytic caps can be higher as long as they fit onto the PCB.

I

For curiosity, here is my first full prototype of the DRO:int4

The DRO:int4's micro-controller can be reprogrammed. But I will offer a service for a programmed uC if the need should be.

If you are willing to invest in a very simple interface or have a ISP for the ATMEL-line of uCs you can use it together with the programming adapter on the board (ISP, 10 pin header near the processor).

After you have the necessary programming interface, download the current version of the controller's firmware here, load it into the programmer's software and flash it into the YADRO-interface. Current version is V0.2c.

Do not forget to set the configuration bits of the uC when programming it. DWEN, EESAVE, WDTON, BODLEVEL0, BODLEVEL1, CKDIV8, CKOUT, SUT0, SUT1, CKSEL0, CKSEL1, CKSEL2 have to be unchecked. Only exception is BODLEVEL2 that has to be checked.
See the screenshot, if checking/unchecking/programm/set/whatever confuses me like it does you.

If you forget to set BODLEVEL2, chances are that you are loosing the configuration after disconnecting the power. BODLEVEL is brown out detection, if you care.

Look twice where pin 1 of the ISP-interface is! This detail of the PCB is not the current layout, but the orientation of the ISP relative to the uC has not changed.

This is the simples programming-interface (called TwinAVR) you can imagine. If you decide to use that one (I haven't, but got good feedback), you can build a simpler interface (compared to the one shown at the TwinAVR's page) that connects to the 10 pin head (SV1):

The "X-PC" connector goes to your PCs Centronics printer port. You just need 2 Rs with 220 Ohms. While programming you have to connect the power supply to the DRO:int4.

Set the configuration and security bits this way:

Programming with PonyProg:

You can download a plan for a ISP-interface and software for programming the uC here. This solution is more complicated but saver. If you intend to do your own projects with ATMELs, I would suggest using this one (or something similar). ISP-compatible interfaces are available at many dealers for around $10.

Set the configuration and security bits this way: