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A lot of people miss this, but if you have an external 3V device, and it's not working on a
certain pin, make sure you're not using a pin with a Schmitt Trigger input buffer.
A pin with a TTL input buffer should work fine with the 3V input if VDD >= 4.5V and <= 5.5V.
A Schmitt Trigger input needs ~0.8 * VDD to meet the input logic 1 threshold.
The comparator trick is cool too, but you might fix it by just switching to a TTL input.
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Ha ha some good ideas i like the comparator hack, i may have to try that as a test to see just if it is a level issue, as i would like to keep those pins free for the pwm.
Pic is 18f2550 so it has them, and I am running it at 5v, the phone/dsm module is 3v but 5v wont harm it.
I have tried input on both port b and C and tried with and without pullups enabled.
I will try the HW uart again with inverted as i am unsure of the stream polarity.
Heres the start of my code as a test etc and to show the configs I have
Code:;DEFINE RESET_ORG 800h ;DEFINE INTERRUPT_ORG 808h define OSC 48 ;dEFINE LOADER_USED 1 ; first four lines to fix broken pbp246 UIR VAR BYTE EXT UIE VAR BYTE EXT UEIE VAR BYTE EXT UEIR VAR BYTE EXT INCLUDE "MODEDEFS.BAS" include "c:\dtusbsvc.pbp" ' would not know what to do without them ! ' setup serial hardware comms DEFINE HSER_RCSTA 90h DEFINE HSER_TXSTA 20h ; try 24 if errors DEFINE HSER_BAUD 9600 DEFINE HSER_EVEN 1 DEFINE CHAR_PACING 1000 ' slow things a little DEFINE HSER_CLOERR 1 ' automatic clear overrun error ' DEFINE HSER_SPBRG 25 ' let picbasic set it from the baud def above DEFINE ADC_CLOCK 1 DEFINE ADC_BITS 8 DEFINE ADC_SAMPLEUS 10 ADCON1 = %10000011 ; not sure lol CMCON = 7 ' Disable Comparators INTCON2.7 = 0 ; should enable portb pullups. TRISA = 3 ; configure AN0 an1 as an input trisb = 255 trisc=255 tempx var byte ; temps.. tempy var byte ; temps.. loop: hserout ["atd123",13,10] for tempx=1 to 2 ; look for 2 chars from it for ''ok'' serin portb.7,n9600,10,tlable,tempy tlable: ; gosub send tempy to usb to pc terminal next goto loop
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What do you get with: serin portb.7,T9600,tempx,tempy
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OK its gone from bad to worse.....
On the downside my internet is down so I only have this mobile phone, but I have now dusted off my old dual trace scope...
What it Ias shown me is I seem to have a timing error...
I have changed from a 4 to a 20mhz crystal go case It was off freq.
I can't use the scope to check timing accuracy its very old and calibrated.
I can't cut and paste my configs now!
As a rule of thumb, if I use the right settings to clock the pic at 20mhz I would be right with pll/5 to be right for usb.
CAn I get a good 9600 set that way?
How many chars can be transferred in say 10 secs?
The scope shows returning data but it looks like the phone/modem. IS at a different speed
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This is what you need with a 4MHz external
Code:DEFINE OSC 48 @ __CONFIG _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L @ __CONFIG _CONFIG1H, _FOSC_HSPLL_HS_1H @ __CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H @ __CONFIG _CONFIG3H, _PBADEN_OFF_3H & _MCLRE_OFF_3H @ __CONFIG _CONFIG4L, _LVP_OFF_4L & _ICPRT_OFF_4L &_XINST_OFF_4L
Dave
Always wear safety glasses while programming.
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thanks, i'll try that in the morning and report back, my net connections up at the moment! if its still up ion the morning i'll post pics off the scope etc of the data to from the gsm modem/phone.
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Originally Posted by mackrackit
Ok been away from this for a few days, sanity protection etc...
tried that in my 18f2550.inc, all worked except for icprt_off_4l was causing an error, so i will leave that bit out for now.
Am i right in the assumption if i want to also try with a 20mhz crystal then only thing i need change is the plldiv to a 5, and leaving cpudiv as is will still then give me 48mhz clocking?
I have acquired a USB/rs232 dongle from the usual chinese supplys on ebay, I thought it would be pl2303 based inside but its a full 3 chipset device, so looks very reliable, made by targus, app not windows 7 compat, but on xp so...
Anyhow, by plugging this in the folowing manner
usb<----targus232-----<---max232----sniffer wire and spare tx wire
by doing the above and setting xp's device mangler to 9600, i can see on my scope signals fro the targus are very like what i get from the 18f2550, by connecting the 'sniffer wire' to the 18f2550, i can see data from the pic, if i incorrectly set the targus, i dont, so the fail proves that its not autobauding and that when it receives char's at a displayed 9600, it really is 9600
so, looks like the pic is tx'ing correctly, and i with the sniffer wire i can see when i connect the 'gsm unit' to the pic, and tell it to 'atdt123' that it replies with 'atdt123' (echo must be on) then after a pause it sends 'no carrier'
I can not seem to receive the 'no carrier' with the pic, but the sniffer wire proves its being sent back, and at the same data rate, ie 9600
so as i have no hadshaking, either i am misisng the window of opportunity, which i doubt as i have about 3 seconds to prep for it, or the 3v logic is too low to trigger hserin
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Ok I have a small amount of progress...
I have managed to receive a single char!
I did this by connecting the pic to the max232 to the 232/usb dongle and using a comms app....
I got the pic to wait for the char and output its binary value on portb, sure enough, 65 for an A
Problem.....
if i send 'A' then it works, if I send AA or AAA it works, but if I send AAAA ith receives the A and display 65, then goes deaf on me and recieves nothing after that.
buffer overflow and then stalled?
program still running, but it goes deaf as a post, 4 chars and deafness.
It even seems to receive from the 3v gsm unit but says char received is 0, when it should be 'N', and then it goes deaf, no doubt as 'no carrier' is more than 4 chars as above.
surely theres a simple way to resolve this ?
I have set the buffer flag to clear over runs etc, and I read I have a 2 byte buffer, so do 2 hserins before i start the loop each time to clear it, I thought that would be enough....
if i can stop it choking, then i can just leave it running in a loop echoing back allowing me to investigate the probably 3v/5 issue, although using the max232 i dont have that issue at the moment
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