Basic Download Circuit (08M), Swapped serin and ground ?

[lahaye]

Hello,

I am having some trouble with my download circuit:

Symptom: Doesn't work (gives device not found error in Program Editor)

Cause: Well, I don't know (or I wouldn't be posting this ), but I think I might have swapped Ground and Serin (serout laptop to serin Picaxe).
In the Manual 1 Page 5 or 31 it gives the circuit which I replicated. I have used the tech supplies 3,5 mm connectors (as shown in the manual) to connect the serial download cable to the board. In the manual it states "above view" (component side of the board?), with serin (of Picaxe) connected to the pins on the right side of the serial connector. On the track side positions will be reversed so serin will be on the left side.
When I measure the voltage (with connected serial cable) between ground (black lead of multimeter) and serin (red lead of multimeter) I get about - 4,5 V; with or without battery pack connected (I am pretty sure I got those connections right )
I assume I should get a positive voltage. Have I misinterpreted "above view"?

I have build this circuit twice, used two different 08M, checked the circuit for shorts, and downloading programs to a 40X1 (on the RevEd Protoboard) works a treat. The circuit is powered by 3 AA batteries.
Three "untouched" 08M left.

Any suggestions are welcome.

Regards Florian

 

[hippy]

In the manual it states "above view" (component side of the board?), with serin (of Picaxe) connected to the pins on the right side of the serial connector. On the track side positions will be reversed so serin will be on the left side.

That sounds correct to me. With the inlet upwards, viewed from the track side, Serila In on the left, Serial Out in the centre, 0V on the right. ...

                                                  .---------------.
 Viewed from Above                                |               |
                             .--------------------| Serial Out    |
  .--------------.           |       .-----.      |               |
.-|  +  +      O |--2/R--.---|---.---|     |------| Serial In     |
| |  .--.      O |--2/R--'   |   |   `-----'      |               |
| |  |  |   O    |--1/S------'   |     22K    .---| 0v            |
| |  `--'      O |--3/T--.      _|_           |   |               |
`-|  +  +      O |--3/T--{     |   |          |   `---------------'
  `--------------'       |     |   | 10K      |         PICAXE
                         |     |   |          |
                         |     `-.-'          |
                         |       |            |
                       --^-------^------------^-- 0v

Could it be that you have wired up the wrong pairs of the two left and right socket pins ? I usually connect the pairs together.

You can do further tests. Start by looking at PICAXE Manual 1 page 31. This shows how a 9-way D is wired to the PICAXE. Now disconnect the 9-way D from the PC, unplug from the 3.5mm jack socket, and remove the 08M from the socket.

1) With a multi-meter check the resistance between the 9-way pins and the 3.5mm plug. These should be close to zero for the following -

Pin 5 to Tip ( 0V )
Pin 3 to Ring ( PC to Serial In )
Pin 2 to Sleeve ( Serial Out to PC )

2) Plug the cable into the jack socket then measure the resistance between the 9-way pins and the PICAXE socket -

Pin 5 to Leg 8 ( 0V ) Should be near zero ohms
Pin 3 To Leg 8 ( Serial In/0V ) Should be near 10K
Pin 3 To Leg 2 ( Serial In ) Should be near 22K
Pin 2 to Leg 7 ( Serial Out ) Should be near zero ohms

 

[lahaye]

Thank you very much

Good day hippy,

Thank you for your quick and extensive reply.
With the help your checklist, I discovered a mistake in my second circuit (1K in place of 10K). I repaired that (by soldering 10K to 1K... I misplaced my solder wick ) and now I get 32 Ohm on leg 2 (serin). Must have some wiring mistake on that board.

Doesn't matter...
Because:
The first circuit now works. I connected both the 2/R and both the3/T together as you suggested (crystal ball seems to be working today... should I buy some stock?) ... and it works right away.

I did do quiet a lot of R-measurements (to find shorts, cold-junctions, etc.) but I guess lacking a systematic approach it must have escaped my attention.

Now let's see If the first 08M is still alive (I think I applied revers Voltage to that one for a couple of seconds)

Most appreciated

Florian