Homebrew AXE133

tracecom

Senior Member
I have breadboarded the AXE133 circuit as shown on page 5 of AXE133-pmd v1.1, downloaded the AXE133 basic firmware from the PICAXE site, and programmed the 18M2, firmware version 2.B. Of course, a wiring error is possible, but I have checked it multiple times, and cannot find any errors. On power up, I get no greeting message; rather, the top row of the LCD seems to be all pixels lit, and the bottom row all pixels dark.

Any suggestions?

Thanks.
 

Rick100

Senior Member
Hello tracecom,

A couple of things you might check. Make sure you have the download circuit on the breadboard(10k and 22k resistors) and the 100n capacitor. The R/W line on the lcd should be tied low.

Good luck,
Rick
 

srnet

Senior Member
One tip, when your copying a circuit diagram that you know should work, print off a copy, and tick each connection with a marker, as you physically check with a multimeter that the breadboard circuit really does match the circuit diagram.
 

neiltechspec

Senior Member
I have successfully built about a dozen AXE133/4 equivalents, a mix of 20X4, 16X2 & three very large 20X4 LCD's.

I did this because I wanted lower profile & repositioning compared to the rev-ed product where the download socket
sticks out beyond the LCD board which can be annoying, I prefer a 3 pin PCB header. Also allowed additional circuitry on some.

Neil.
 

tracecom

Senior Member
One tip, when your copying a circuit diagram that you know should work, print off a copy, and tick each connection with a marker, as you physically check with a multimeter that the breadboard circuit really does match the circuit diagram.
You are correct. In a complicated build, I always use a highlighter to mark the components and connections as I complete each one. I neglected to do that on this one because I thought it was too simple to require it. And, the other reason I didn't do it was because the drawing I was following didn't lend itself to the procedure.
 

tracecom

Senior Member
I have successfully built about a dozen AXE133/4 equivalents, a mix of 20X4, 16X2 & three very large 20X4 LCD's.

I did this because I wanted lower profile & repositioning compared to the rev-ed product where the download socket
sticks out beyond the LCD board which can be annoying, I prefer a 3 pin PCB header. Also allowed additional circuitry on some.

Neil.
My breadboard is now working as designed. My first impression is that the code is somewhat lacking in features, but I haven't really thoroughly explored it.
 

tracecom

Senior Member
I am trying to get the backlight function working. As a first step, I want to make C.2 (leg 1) of the 18M2 high. The following code from an 08M2 does everything I expect, except make C.2 high. Why? Thanks.

Code:
init: pause 500 ; wait for display to initialise
main:
serout C.1,N2400,(255,%00000100) ; make C.2 high
pause 1000
serout C.1,N2400,(254,1) ; clear display
pause 100
serout C.1,N2400,(254,132) ; move to start (+ 4 spaces) of first line
serout C.1,N2400,("ElecMech") ; output text
serout C.1,N2400,(254,194) ; move to start (+ 2 spaces) of first line
serout C.1,N2400,("Designs, LLC") ; output text
end
 

Rick100

Senior Member
Hello tracecom,

I recall helping someone else with this problem. Here is the thread:
http://www.picaxeforum.co.uk/showthread.php?25521-axe133-outputs

Try breaking up the command to turn on the pin into 2 serout commands, like this.

Code:
init: pause 500 ; wait for display to initialise
main:
serout C.1,N2400,(255) ; make C.2 high
pause 10
serout C.1,N2400,(%00000100) ;
pause 1000
serout C.1,N2400,(254,1) ; clear display
pause 100
serout C.1,N2400,(254,132) ; move to start (+ 4 spaces) of first line
serout C.1,N2400,("ElecMech") ; output text
serout C.1,N2400,(254,194) ; move to start (+ 2 spaces) of first line
serout C.1,N2400,("Designs, LLC") ; output text
end
Good luck,
Rick
 

tracecom

Senior Member
Rick,

Once again, you are correct. Thanks again. I have to wonder (rhetorically, I suppose) why that hasn't been corrected either in the firmware, or at least in the documentation.

On a related subject, while I was troubleshooting this issue, I discovered that my LCD (JHD 162A) would stay powered up even with the ground removed from pin 2. Apparently, the ground on pin 5 is sufficient to keep the LCD on. Is that correct, and have you seen that in other LCDs?

Thanks.
 

tony_g

Senior Member
Hello tracecom,

I recall helping someone else with this problem. Here is the thread:
http://www.picaxeforum.co.uk/showthread.php?25521-axe133-outputs

Try breaking up the command to turn on the pin into 2 serout commands, like this.

Code:
init: pause 500 ; wait for display to initialise
main:
serout C.1,N2400,(255) ; make C.2 high
pause 10
serout C.1,N2400,(%00000100) ;
pause 1000
serout C.1,N2400,(254,1) ; clear display
pause 100
serout C.1,N2400,(254,132) ; move to start (+ 4 spaces) of first line
serout C.1,N2400,("ElecMech") ; output text
serout C.1,N2400,(254,194) ; move to start (+ 2 spaces) of first line
serout C.1,N2400,("Designs, LLC") ; output text
end
Good luck,
Rick
yep that one got me, it was annoying when the code given in the reference doc didnt work but as rik100 pointed out seperating the command for the outputs did the trick :cool:
 

tracecom

Senior Member
I wanted to ask about this again. While I was troubleshooting this issue, I discovered that my LCD (JHD 162A) would stay powered up even with the ground removed from pin 2. Apparently, the ground on pin 5 is sufficient to keep the LCD on. Is that correct, and has anyone seen that in other LCDs?
 

inglewoodpete

Senior Member
CMOS chips usually have ESD protection circuitry built into them to minimise the risk of damage due to high voltage discharges into their gates (inputs). The most common type of protection is a pair of diodes connected in a normally reverse-biased configuration between Vcc, input and 0v (ground). While this offers quite good ESD protection, it results in some side effects in certain circuit configurations.

Rather than me rewriting the book on ESD protection diode side effects, have a read here. Focus more on the protection diodes and circuit sketches about 1/3 down the webpage.
 

tracecom

Senior Member
CMOS chips usually have ESD protection circuitry built into them to minimise the risk of damage due to high voltage discharges into their gates (inputs). The most common type of protection is a pair of diodes connected in a normally reverse-biased configuration between Vcc, input and 0v (ground). While this offers quite good ESD protection, it results in some side effects in certain circuit configurations.

Rather than me rewriting the book on ESD protection diode side effects, have a read here. Focus more on the protection diodes and circuit sketches about 1/3 down the webpage.
Thanks. I believe that is the answer.
 
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