Unstable 18f458

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- 1st October 2011, 12:19
pkoliver

Unstable 18f458

Hi
I am migrating from 16f887 to 18f458 in a motor control application. both chips work my dev board (labx 2) and also in my prototype rig
until the motor is connected. then the 16f is ok but the 18f has random resets will run sometimes for 20 seconds others 1 second.
I have determined that the problem is complete reset. I also checked with oscilloscope vss is good and no noise on vdd. Lower current to the motor seemed to lengthen run time. Very frustrating. What things can cause the pic to reset.
regards Paul
- 1st October 2011, 13:34
mackrackit

Re: Unstable 18f458

A voltage drop could cause a reset. Are the motors using the same power supply as the MCU?
How are the configs set for the 18F?
- 2nd October 2011, 12:37
pkoliver

1 Attachment(s)

Re: Unstable 18f458

Thanks for the reply Mackrachit
The only change to config was to change to HS in the inc file. The brown out is set to enable and 2 v. I tested with brown out disable with no effect. Testing for power drops shows no problem. I use a !2 v supply from a bench supply and a 7805 5v reg. A further problem has occurred on one occasion. The eeprom data for approx 32 registers changed to 00. See photo of my prototype set up. The bipolar stepper drivers are close to the pic. Are 18f very delicate compared to 16f
regarding em interference. Please treat my as pic novice as only been playing for 12mths (lots of fun though)

Attachment 6019
- 2nd October 2011, 14:42
cncmachineguy

Re: Unstable 18f458

If you have an scope, watch the ground for spikes. I expected to see some caps in the area of 47uF but cant make them out on your board. Stepper drives are NOISEY!!! You may be getting a spike on ground enough to cause the pic to reset.
- 2nd October 2011, 14:46
mackrackit

Re: Unstable 18f458

Yup, what he said.
A sprinkling of caps where ever you can fit them in. Most important have them as near to the MCU VSSs and VDDs as you can.
- 3rd October 2011, 11:20
pkoliver

1 Attachment(s)

Re: Unstable 18f458

Hi
see picture with suggested caps. thanks both for the advice. Now working fine. I did see the spikes on ground and moved my vss connection point to the ov pin on the 7805 before my post and had a small improvement. My scope showed this point to be clean.(it is a PC based scope. keep my good scope at work. May not be quick enough to trigger on the spike). But probably not clean enough. You can only find out what you don't know by doing something first and apparently circuit design isn't my strong point.

cncmachineryguy How are you involved in with cnc. I make my living with cnc machines. look up my business at www.abcoprecision.com.au

now to get the 40mhz osc to work

Attachment 6027
- 3rd October 2011, 11:41
mackrackit

Re: Unstable 18f458

Quote:

now to get the 40mhz osc to work

Use a 10MHz crystal or resonator then set the config to HS4.
- 3rd October 2011, 12:39
pedja089

Re: Unstable 18f458

It would be better to use 100nF ceramic cap. They have much better(10X lower or even more ) ESR than elco.
- 3rd October 2011, 13:26
pkoliver

Re: Unstable 18f458

hi

any problem using both 47uf and 100nf.

also now am losing some data when loading map data to codespace from serial ( max 232) . going to bed . late here in oz. will test in lab-x2 to see if serial in is ok tomorrow and then chase down my proto board probs.
good nite

regards Paul
- 3rd October 2011, 15:37
mackrackit

Re: Unstable 18f458

Quote:

also now am losing some data when loading map data to codespace from serial

You need to post the code and clarify some.
- 3rd October 2011, 16:08
cncmachineguy

Re: Unstable 18f458

Paul, Can you please post the drive chip you are using for the steppers? I can't quite make out the part number. I think the 47uF caps should be as close to those chips as possible but would like to double check the datasheet.

Side note - I have a small contract job shop. 4 VMC's and a lathe. But my true love is building machines and controlling them. My user name is a left over from a long time ago in another forum, so I just use it now for easy remembering to me. :)
- 4th October 2011, 13:24
pkoliver

1 Attachment(s)

Re: Unstable 18f458

Hi again

The stepper driver ic L298n with L297 controller ic.

When upload if maps to pic method is as follows.
1 send numeric value 1 to select case 1 load map data
2 pc waits to receive "R" (pic ready)
3 send first packet "AxxxxBxxxx" A= address B= data
4 write data to eeprom or code space depending if A value < 128
5 send "s" to PC
6 wait for next packet
7 if "A9999" received end of data transfer

Sometimes upload is fine.
There is 13 blocks of 256 words that make up the map data and when I view the pic memory I can see areas with rows of zeros and some 00001 and 00002 where a value of 55 should be. this fail area is for 4 memory rows and then comes good. When upload of map is in progress the stepper driver is set to disable and .12 amp of draw only from power supply in this state so noise at this time is unlikely.

see picture taken from meProg The row with 11111 is a partition only and npt read. Below that the values should be progressively larger than the 45 values that are correct.

Beginning to suspect the usb to serial adapter. This is difficult to see because if the data string is not AxxxxBxxxx then error occures. so the error is only in the values after B as the correct addresses are written . It is as if the charge pump runs out in the pic and then recovers. Also the defective area is mainly in a similar area. Tricky hey

Attachment 6033

Code:

'-------------Main Code------------ DEFINE HSER_RCSTA 90h DEFINE HSER_TXSTA 24h DEFINE HSER_BAUD 76800 DEFINE HSER_EVEN 1 DEFINE OSC 20 INTCON2.7=0 ' Enable PORTB pull-ups 18f458 TRISB = 110000 PORTB = 000001 loadlamp1 var word loadlamp2 var word mapflag var byte data1 VAR word location VAR word computercontrol var byte computerpos VAR word connect var byte '------------------------------------------------------------------------------------------------------ mainloop: if RCSTA.1 then ' Overrun error? used to reset input ready to recieve RCSTA.4=0 ' clear it RCSTA.4=1 endif if PIR1.5 then gosub loaddata 'if a chaeacter has arived at serial in the PIR1.5 will = 1 goto mainloop: '------------------------------------------------------------------------------------------------ Loaddata: hserin [dec1 data1] 'read case number from pc 1 = load 2 = computer control 4 = connection extablished 5 = disconnect select case data1 case 1 loadlamp1 = 0 loadlamp2 = 6 HSEROUT ["R"] 'pic ready to recieve Load2: HSERIN 5000,TimeOut2,[WAIT("A"),hex4 location,WAIT("B"),hex4 data1] 'if next packet not recieved in 5 sec then go timeout 2 loadlamp1 = loadlamp1 + 1 'led flash while data transfer in progress if loadlamp1 > loadlamp2 then PORTB=PORTB << 1 if loadlamp1 > loadlamp2 then loadlamp2 = loadlamp1 + 6 IF PORTB.3 THEN PORTB = 000001 if location = 9999 then goto TimeOut2 'when A9999B0000 sent from pc data transfer finished if location > 128 then goto cs 'codespace addresses are always greater than 128 write location , data1.lowbyte write location+128 , data1.highbyte HSEROUT ["S"] 'please send next data packet GOTO Load2: cs: Writecode location ,data1 HSEROUT ["S"] 'please send next data packet GOTO Load2 TimeOut2: if location = 9999 then HSEROUT ["Recieve ok"] else HSEROUT ["F"] 'fail load set to pc endif HSERIN 20,TimeOut3,[WAIT("recieve nill")] 'this is needed to final clear PIR1.5 and stops main loop jump to loaddata TimeOut3: PORTB = 000001 RETURN case 2 HSEROUT ["R"] computercontrol=1 HSERIN 5000,TimeOut2,[WAIT("P"),dec3 computerpos] location = 9999 goto TimeOut2 case 3 HSEROUT ["R"] computercontrol=0 location = 9999 goto TimeOut2 case 4 HSEROUT ["C"] connect=1 location = 9999 goto TimeOut2 case 5 HSEROUT ["D"] connect=0 location = 9999 goto TimeOut2 end select return end