Products > Test Equipment
Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
m k:
With unlimited binary data there are no other way than external end or time out.
If data is #13#13 the thing is clear and no extras are needed.
On the other hand if data is #0#0#0 there is no way to know when it ends without something external.
Trigger from NI-488.2M manual
--- Code: ---Send(0, fluke, "VAC; AUTO; TRIGGER 2; *SRE 16", 29L, NLend);
sum = 0.0;
for (m=0; m < 10 ; m++) {
Send(0, fluke, "*TRG; VAL1?", 11L, NLend); // Trigger the Fluke
WaitSRQ(0, &SRQasserted); // Wait for the Fluke to assert SRQ
ReadStatusByte(0, fluke, &statusByte); // Be sure that the MAV is set
Receive(0, fluke, buffer, 10L, STOPend); // Read the measurement
buffer[ibcnt] = '\0';
printf("Reading : %s\n", buffer);
sum = sum + atof(buffer);
}
--- End code ---
--- Code: ---ibwrt (dmm, "F1R0S2T4", 8);
for (sum=0, x=0; x <= 10; x++) {
ibtrg (dmm);
ibrd (dmm, rd, 13);
sum = sum + atof(rd);
}
--- End code ---
STOPend(int) is defined as EOI or EOS, 0x0 - 0xff there will terminate there.
Second code is getting 13 bytes.
joeqsmith:
--- Quote from: dietert1 on February 11, 2021, 04:55:55 pm ---...
After two hours or so (with roughly a million of readings) i would find 0D and 0A in the binary data where it doesn't belong.
...
Regards, Dieter
--- End quote ---
Even with the serial port, I see it do some pretty strange things. Some times it starts out slow then speeds up. I've had the meter get to a point where I could not do anything but power cycle it to shake it loose. But, I am playing with some odd conditions and their software group may not have considered them. Under normal use, it seems to be fairly reliable.
You ordered the application note. Nice. I haven't had time to hunt for it.
--- Quote ---With unlimited binary data there are no other way than external end or time out.
--- End quote ---
Sure you can. Knowing something about the data is the key and in this case, the data is very slow so there is plenty of time to lock to it.
SilverSolder:
I got 5x 2764 EPROMs here, marked Texas Instruments TMS 2764-20JL LHP 8831 ... eBay.
The weird thing is, I can program them and verify them in the programmer. But they don't work in the controller board!?!
I then tried erasing the old EPROMS in my brand new el-cheapo EPROM eraser. 1/2 hour was enough to erase the chips, next time I'll try 20 minutes and see how good the lamp is...
I then programmed the old EPROMS with the version 506/607 software - success! Meter started right up.
Is there anything I could be doing wrong with the TI EPROMS that would make them verify on the programmer, but not run in the actual circuit?
SilverSolder:
--- Quote from: dietert1 on February 11, 2021, 04:55:55 pm ---I also gave up on the '!' for the time being, since it did not run reliably. After two hours or so (with roughly a million of readings) i would find 0D and 0A in the binary data where it doesn't belong.[...]
--- End quote ---
Couldn't that happen accidentally, if the voltage happens to have 0D 0A in the measured value?
srb1954:
--- Quote from: SilverSolder on February 12, 2021, 03:04:59 am ---
I got 5x 2764 EPROMs here, marked Texas Instruments TMS 2764-20JL LHP 8831 ... eBay.
The weird thing is, I can program them and verify them in the programmer. But they don't work in the controller board!?!
I then tried erasing the old EPROMS in my brand new el-cheapo EPROM eraser. 1/2 hour was enough to erase the chips, next time I'll try 20 minutes and see how good the lamp is...
I then programmed the old EPROMS with the version 506/607 software - success! Meter started right up.
Is there anything I could be doing wrong with the TI EPROMS that would make them verify on the programmer, but not run in the actual circuit?
--- End quote ---
Have you checked that the EPROM programmer set-up is correct (voltages, pulse widths etc) for the TMS2764?
If the parameters are not quite right the programming might be marginal enough that the data verifies correctly immediately after programming but fails later under slightly different conditions. Most good EPROM programmers try to weed out marginal programming by re-verifying the data under high and low Vcc conditions. A cheap programmer might not do that.
You could check the data retention by setting the EPROMs aside for a day and then re-verifying to see if any bits have decayed.
Lastly you should consider whether the chips purchased via eBay might be counterfeit or production rejects that have been relabelled as a different speed grade.
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