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DIY Tait Programmer with WxPic

PostPosted: 05, 2011 Sep Mon 8:46 am
by vlady
I have built (on bread-board) a Tait programmer as per

I am testing the Tait programmer/WxPic with a PIC16F84A (as I have a PicKit2 that I can independently check the state of the PIC16F84A), however, the aim is to use the DIY Tait programmer with PIC16C711 (which is not supported by PicKit2, and of which I was given 100 x PIC16C711).

I am using the following settings with WxPic in the "Interface" tab:
Interface Type = Tait, 7407(Driver)+PNP Transistor
Port = LPT1
Extra delay on both the clock and data lines is 6uS (which is the default?) - I also tried with both delays = 0

When I have WxPic running first and then power-on the DIY Tait programmer, I get the following in the message window:
Failed read back of DATA line (LOW) !
18:22:27.817 WARNING: Could not initialize programmer !

If I have DIY Tait programer powered-on and then start WxPic, I get the following in the message window:
18:23:26.702 Info: Parsing argument from command line
18:23:27.152 Info: Loading definitions for "PIC16F84A" from C:\Program Files\WxPic\devices.ini .
18:23:27.152 Info: PIC16F84A added and tested by FENG3
18:23:27.152 Parsed "C:\Program Files\Microchip\MPLAB IDE\Device\" : found 10 bit combinations in 4 configuration bit groups .
Failed read back of DATA line (LOW) !
18:23:28.24 WARNING: Could not initialize programmer !
Testing: delay(500ms) took 0.51 seconds, timer_freq=3.5795 MHz ... ok

Using the Interface Test controls, I get the following voltages on the indicated pins of a PIC16F84A connected to the DIY Tait Programmer:
Vpp (+13v) when "ticked" pin 4 = 13.2v, when "unticked" pin 4 = 0v
Vdd on/off when "ticked" pin 14 = 4.9v, when "unticked" pin 14 = 0v
Clock when "ticked" pin 12 = 2.3v, when "unticked" pin 12 = 0v
Data to PIC when "ticked" pin 13 = 2.3v, when "unticked" pin 13 = 0v
pin 5 of the PIC16F84A is also connected to ground, I have also tried the above with and without a 10K resistor from pin 10 to ground as well

This seems to indicate I am getting the correct signals to the correct pins, but I cannot get WxPic to report that the programmer is initialised, and when trying to programme code/data get verify error.

Any help in advising what I should change/measure to get the circuit/WxPic operating (or perhaps which other programmer circuit I should try with a view to eventually using PIC16C711) is appreciated.

Thanks in advance

Re: DIY Tait Programmer with WxPic

PostPosted: 05, 2011 Sep Mon 10:18 pm
by admin

Check if ACK pin (or 7407 pin 10) correctly toggles when DATA is checked/unchecked. The diagnostics from WxPic seems to indicate that the pin does not switch on or off (what is the status of the IN pin in the interface panel?)

You can also test the interface without any PIC inserted to avoid any problem coming from a bad PIC (but in this case I believe this is not the origin of the problem).


Re: DIY Tait Programmer with WxPic

PostPosted: 06, 2011 Sep Tue 12:31 pm
by vlady

When "Data to Pic" is toggled on the WxPic interface, the voltage on pin 10 of the 7407 toggles between 4.95v (check box ticked) and 0v (check box unticked). Below this checkbox the "Data In = 1" is displayed and does not change when "Data to Pic" is toggled.

When I remove the Pic from the circuit I still get "WARNING: could not initialiser programmer".


Re: DIY Tait Programmer with WxPic

PostPosted: 06, 2011 Sep Tue 7:10 pm
by admin
So the error origin may be in decreasing order of probability:
- The pin 10 of the 7407 is not connected on pin 10 of the DB25 (may be connected to another one)
- The DB25 connector is not well plug (it happen to me once that the weight of the cable had slightly pulled out the plug).
- The "Tait 707(driver) + PNP transitor" interface type is not selected
- The LPT port has died (its ACK input no longer works)

I see no other possibility because I just tested WxPic with this interface type with a fake interface (just connect D0 to ACK => DB25 Pin 2 to Pin 10). And WxPic says that the Interface is working.