DATA transmission/receiving using SCR Radio modules.

ericgibbs · Feb 3, 2017

hi,
regopmode address 0x01

data bits
0 = FSK/OOK : change allowed in SLEEP Mode ONLY
01 = OOK
0 =Res
1 = LF mode
101 = rec mode rx

0,01,0,1,101 == 0x2D

Is the unit in Sleep Mode.?

E

camerart · Feb 3, 2017

ericgibbs said:
hi,
regopmode address 0x01

data bits
0 = FSK/OOK : change allowed in SLEEP Mode ONLY
01 = OOK
0 =Res
1 = LF mode
101 = rec mode rx

0,01,0,1,101 == 0x2D

Is the unit in Sleep Mode.?

E

Hi Eric,
You've come to the same result 0x2d, good.
Have you looked at the Rx program in #1? Hopefully, I have set-up correctly, sleep then write RX.
Must be somethingelse?
C.

ericgibbs · Feb 3, 2017

hi,
Used in your other thread:

"The SPI interface gives access to the configuration register via a synchronous full_duplex protocol corresponding to CPOL=1 and CPHA=0 in Motorola/Freescale nomenclature. Only the slave side is implemented."

E
My plot shows...using your program

camerart · Feb 4, 2017

ericgibbs said:
hi,
Used in your other thread:

"The SPI interface gives access to the configuration register via a synchronous full_duplex protocol corresponding to CPOL=1 and CPHA=0 in Motorola/Freescale nomenclature. Only the slave side is implemented."

E
My plot shows...using your program

Hi Eric,
Yes, this is what I get too. It's as near to the Oshonsoft SPI timing diagram.
It looks as though the Oshonsoft NSS CS runs low then goes high, then as it goes low again starts the sequence. I couldn't get it to run as my yellow line on the attachment.
I am able to change the MODE as long as it isn't RX. I'll keep trying different cominations.
C

ericgibbs · Feb 4, 2017

hi C,
The point I am raising is the clock sense.
Image 002 is the sense that the SX expects according to your earlier posts.
Image003 is what you are using to communicate with the SX. PORTC.3

E

EDIT:
Look at this link.
https://hackaday.com/2016/07/01/what-could-go-wrong-spi/

camerart · Feb 4, 2017

Hi Eric,
Much to read and understand!
Using the set-up shown on my DOC where in simple terms, after the point where the NSS going LOW the SCK goes HIGH/LOW repeatedly in time with the MOSI going HIGH/LOW. I'll clean up my understanding later. On my DATA sheet CPOL =0 as shown in my DOC, on your last post your DATA sheet show CPOL=1, unless I'm misunderstanding.

In the mean time, there are many combinations to grapple with.
1/ If I WRITE 0x0d in RegOpMode OOK-0, FSK-00, RES-0, LOW-1, RX101 The result on the READ LCD is 45 = 0x2d which is what we want.
This is receiving signals as I switch on the TX.

From a quick scan of your SPI link, it reminds me that there is a fascility to synchronise the signal with DIO1/DCLK, I've yet to try this.
C.

camerart · Feb 4, 2017

Hi,
I changed the TX inside the 'mainloop' to simple on/off each second. On the RX, an oscilloscope on DATA shows a signal being received but is not transfered to the PIC because of the 3.3V-5V mismatch. This should be ok, once I've got 3.3V PICs.
The received signal is broken, which could be that I had to use FSK instead of OOK.

EDIT: Tried WRITING 0x2d to RegOpMode on RX. The LCD shows 0x2c, but it is receiving ok.
Regarding the broken received signal, this could be because it's a tone???
C.

ericgibbs · Feb 4, 2017

hi,
On the SDI line do you have a 10k pull up to +5v.?

I don't understand
Regarding the broken received signal, this could be because it's a tone???

E

camerart · Feb 4, 2017

ericgibbs said:
hi,
On the SDI line do you have a 10k pull up to +5v.?

I don't understand
Regarding the broken received signal, this could be because it's a tone???

E

Hi Eric,
I have a thought at the back of my mind regarding the 10K pull up on one of the SPI connections. I thought it was MISO/SDO though. I put it on the back burner, because I had to put 22K resistors in series on all SPI connections, instead of matching the voltages. I'll get some 10K resistors for the new 3.3v circuits.

The TX/RX signals are tones as you would hear with Morse. I just connected an earphone to the DATA pin on the RX and it sounds like the end of a record pulsing on and off in time with the TX.
C.

camerart · Feb 5, 2017

ericgibbs said:
hi,
On the SDI line do you have a 10k pull up to +5v.?

I don't understand
Regarding the broken received signal, this could be because it's a tone???

E

Hi Eric,
I found a note on the program reminding me about a 10K pull up on the MISO line, so depending on whether your questions was from the SX perspective or the PIC perspective, that may be the answer. This is why I've adopted MISO and MOSI terminology
C.

ericgibbs · Feb 5, 2017

hi C,
How are you down level shifting between the PIC at 5v and the SX at 3.3v.?
C select, Clock and SDO [ MOSI]
E

camerart · Feb 5, 2017

ericgibbs said:
hi C,
How are you down level shifting between the PIC at 5v and the SX at 3.3v.?
C select, Clock and SDO [ MOSI]
E

Hi Eric,
The Sx has clamped inputs at 3.3v, and following a suggestion for the test circuits added 22K resistors in series on all lines. This is working, but the RX cannot switch the PIC input because of the low voltage.
Next step is to order surface mount components, then they will be voltage matched (not sure about the LCD though) . Some of the surface mount components are very small, so I'm trying to figure out the larger ones.
So far I've made my own circuits photographically, but perhaps not this time, as the PIC is 18mm long with 14 pins each side.
C.

camerart · Feb 15, 2017

Hi,
I've made a new test circuit using fuse wire as tracks (spaghetti wiring) Using an 18LF2520 surface mount PIC connected directly to the SX1278. Generally the same circuit as posted.

I had a few issues with 3.3V programming, but after setting MPLAB.IPE to 3.375V and changing the Pickit3 external power supply to 3.3V, things settled down.

I bought a digital analyzer, see image: While it shows timing, it doesn't show slopes in the square waves.

The circuit is now working as TX. Next see if I can get it to RX.

C.

ericgibbs · Feb 15, 2017

hi C,
Ref your PM.
If I follow the SX datasheet spec for the SPI, it suggests that the clock should be High at rest, going low for the Clock period. [you show it the opposite sense]

You say that you can Write/Read the SX registers OK with the Clock as shown in your image, if that is the case, I would move onto the next stage of the project.

E

camerart · Feb 16, 2017

ericgibbs said:
hi C,
Ref your PM.
If I follow the SX datasheet spec for the SPI, it suggests that the clock should be High at rest, going low for the Clock period. [you show it the opposite sense]

You say that you can Write/Read the SX registers OK with the Clock as shown in your image, if that is the case, I would move onto the next stage of the project.

E

Hi Eric,

I've attached a clip from my SX1278 data sheet. To me it looks as if the clock/SCK is low at rest and goes high for the clock period.

C.

ericgibbs · Feb 16, 2017

hi C,
You did post in an earlier post:
"The SPI interface gives access to the configuration register via a synchronous full_duplex protocol corresponding to CPOL=1 and CPHA=0 in Motorola/Freescale nomenclature. Only the slave side is implemented."

Which suggests a Clock High at rest, going low when clocked.

Your clip in #95 states CPOL=0.

One of the statements is incorrect.
As the SPI works OK using CPOL=0 I would say the 1st statement is wrong.

E

camerart · Feb 16, 2017

ericgibbs said:
hi C,
You did post in an earlier post:
"The SPI interface gives access to the configuration register via a synchronous full_duplex protocol corresponding to CPOL=1 and CPHA=0 in Motorola/Freescale nomenclature. Only the slave side is implemented."

Which suggests a Clock High at rest, going low when clocked.

Your clip in #95 states CPOL=0.

One of the statements is incorrect.
As the SPI works OK using CPOL=0 I would say the 1st statement is wrong.

E
View attachment 104333

Hi Eric,
I've been through all of my module PDFs and they all show See attached: I don't know where I got the first statement from, but as you say it is incorrect.

There is an issue when I try to program for RX. As I've now got 5x SX1278s all with the same issue, it must be a rule I've broken, which I'll have to find. The problem is: When programming TX the LCD reads what I have programmed, and reports TX, then transmits ok. When I try RX, the LCD never reports RX, but changes it to FSRX. which may be correct, I'm not sure.
C.

camerart · Feb 17, 2017

Hi,
Looking at the logic analyser readings See attached:
STANDBY shows the RegOpMode setting 0x01, plus the write bit 10000001, then the reading which is STANDBY including the OOK and LOW Frequency bits 00101001 written with MISO, then it is reflected in the MOSI reading.

TX shows RegOpMode then TX in MOSI reflected in MISO

RX shows RegOpMode then RX in MOSI, but incorrectly reflected in the MISO reading.

I realise that the logic analyser doesn't shows square wave errors, but does appear to show some switching accuracy, but the readings appear to show that Oshonsoft is programming the PIC correctly.

C.

camerart · Feb 18, 2017

Hi,

It's been pointed out to me that the missing bit when the PIC controls the SX1278 with RX is most likely to be the SPI timing.

C.

camerart · Feb 18, 2017

Hi,
I am trying to set-up CLKOUT from the SX1278 as OSC IN on the 18LF2520. See attached: It shows this is advisable for synchronisation.

At the moment the PIC is not oscillating, so something's wrong.

Here's the program:

I'm a bit vague about all of the settings.
C.

DATA transmission/receiving using SCR Radio modules.

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