Cheap Idea for a DRO

[BillTodd]

ISTR you can fit one or more PICs as required.

I'm getting to understand your assembly code

Congratulation John - that's more than I ever did :LOL:

From memory, the Txsyn timing is a simple grab a slot when ready affair with a different delay based on chip position to help prevent collisions.
(i.e. if Txsyn = hi, delay X.Y,Z or W recheck Txsyn if hi, pull txsyn low and transmit)

Is the vernier being switched into fast mode correctly? Different makes/types of scale have different clk/data line switching sequences so some don't work with out mod'ing the code


Are you powering the scales from the interface or the on-board cell? (I replaced the cells with a ~1uF SM cap) What voltage are you ghetting across the PSU red-led?

The serial port is running at 115,200 baud, so screening and good earthing is advisable. And, it derives its -Ve from the PC so, just check that's working OK.

[1113562]

ISTR you can fit one or more PICs as required.

I tried this as you can see in the photo as it sort of worked so I assumed the design does not require all PICs in place

Is the vernier being switched into fast mode correctly? Different makes/types of scale have different clk/data line switching sequences so some don't work with out mod'ing the code

I think it is I being switched - I get a small hi symbol appearing on the LCD display. The zero switch on the vernier doesn't zero when connected to your interface it just seems to make it switch between fast and slow mode. I will try another vernier I have which is a later BCD output model with a 2032 3V button cell battery.

Are you powering the scales from the interface or the on-board cell? (I replaced the cells with a ~1uF SM cap) What voltage are you ghetting across the PSU red-led?

Yes I'm powering from the interface board. I don't have a cell in place or a cap. I'll try and put a 1uF in the place of the battery cell, that may stabilise things. Whats your suggestion for the 3V verniers as I note the signals are still only 1.5 v p-p despite the 3V cell? I measured my LED Vernier power output as 1.63V, its bit hi but thats due to the LED i'm using. Do you think I should try and get this back to 1.5V?

The serial port is running at 115,200 baud, so screening and good earthing is advisable. And, it derives its -Ve from the PC so, just check that's working OK.

As you can see i've used a crap bit of ribbon for this cable but ist only about 20" long. I must try to improve this with a screened cable. I am getting a good 0V reference from the PC. I'll look at all this later with a scope to see whats going on, in the end its bound to be an analogue thing.

Thanks for all your help. John

[1113562]

Here is an update to things but to make it easy I have attached a word doc with embedded pics. It describes some scope measurements of the signals on the interface board. I hope it is readable.