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MiniWireless with RFM98W schematics  XML
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cambazz



Joined: 22/03/2015 01:37:43
Messages: 5
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Hello,

I was unable to find schematics for the anarduinos with RFM98W.

I am assuming it is like:

* Arduino RFM95/96/97/98
* GND----------GND (ground in)
* 3V3----------3.3V (3.3V in)
* interrupt 0 pin D2-----------DIO0 (interrupt request out)
* SS pin D10----------NSS (chip select in)
* SCK pin D13----------SCK (SPI clock in)
* MOSI pin D11----------MOSI (SPI Data in)
* MISO pin D12----------MISO (SPI Data out)

like in radiohead libraries documentation. Is this devices connection to anarduino exactly the same?

Also, is it possible to use another spi device on the anarduino?

best regards

Also could someone explain why it says we have to attach antenna? (will the PA burn out if there is none?)
stevech



Joined: 07/07/2014 18:07:27
Messages: 91
Offline

Antenna absent - I've done it often when doing desktop testing and range isn't important.

second SPI device wired up to board... here are the considerations
- added SPI device needs its own unique chip select (SS) bit
- The radioHead interrupt service routine will use the SPI port unaware that there may have been a concurrent SPI by the second SPI device

As to the second point, there are two ways I know of to deal with this "mutual exclusion" access to a shared device (that being the SPI controller).
1. When the second device starts to use the SPI port, it must first cause the radio to switch to the idle mode where the receiver and transmitter are "off" and cannot interrupt. The SPI can then be used for the second SPI device without risk of a radio's interrupt trying to also use the SPI port. Downside: If the second device hogs too much time, an message may be missed. If the message uses the RadioHead reliable datagram protcol, the sender will delay and retry and hopefully the second device will have finished its uses of the SPI and reenabled the receiver by calling available().
2. Arduino (latest) libraries have a function "SPI Transactions". With this, a program contends for use of the SPI port. When the transaction is permitted, the other (radio) usage will have its interrupt disabled until the transaction is finished. This transaction concept does NOT work well with real-time, perishable data as is the case for wireless messaging. Transactions work well for non-real-time such as SPI flash memory, LEDs, and so on.

I use approach (1) due to the real-time nature of wireless.

Ideally, one uses an MCU with two SPI ports as are common on the small ARM boards like Teensy 3.x and Teensy LC. This avoids the contention.


This message was edited 1 time. Last update was at 22/03/2015 17:00:53

cambazz



Joined: 22/03/2015 01:37:43
Messages: 5
Offline

Hello,

The anarduino module with rfm98w is undocumented at this point. For example the DIO0 and DIO5 on the RFM98W module, are connected to pins 4 and 2
which i had to figure out by measuring.

There are many pins on the RFM98 module. How can i figure out which pins it is connected to?

Best regards,
-C.B.


stevech wrote:Antenna absent - I've done it often when doing desktop testing and range isn't important.

second SPI device wired up to board... here are the considerations
- added SPI device needs its own unique chip select (SS) bit
- The radioHead interrupt service routine will use the SPI port unaware that there may have been a concurrent SPI by the second SPI device

As to the second point, there are two ways I know of to deal with this "mutual exclusion" access to a shared device (that being the SPI controller).
1. When the second device starts to use the SPI port, it must first cause the radio to switch to the idle mode where the receiver and transmitter are "off" and cannot interrupt. The SPI can then be used for the second SPI device without risk of a radio's interrupt trying to also use the SPI port. Downside: If the second device hogs too much time, an message may be missed. If the message uses the RadioHead reliable datagram protcol, the sender will delay and retry and hopefully the second device will have finished its uses of the SPI and reenabled the receiver by calling available().
2. Arduino (latest) libraries have a function "SPI Transactions". With this, a program contends for use of the SPI port. When the transaction is permitted, the other (radio) usage will have its interrupt disabled until the transaction is finished. This transaction concept does NOT work well with real-time, perishable data as is the case for wireless messaging. Transactions work well for non-real-time such as SPI flash memory, LEDs, and so on.

I use approach (1) due to the real-time nature of wireless.

Ideally, one uses an MCU with two SPI ports as are common on the small ARM boards like Teensy 3.x and Teensy LC. This avoids the contention.


empeka



Joined: 21/12/2014 05:56:01
Messages: 18
Offline

cambazz wrote:Hello,

The anarduino module with rfm98w is undocumented at this point. For example the DIO0 and DIO5 on the RFM98W module, are connected to pins 4 and 2
which i had to figure out by measuring.

There are many pins on the RFM98 module. How can i figure out which pins it is connected to?



D2 RFM interrupt
D3 rtc interrupt
D5 flash mem SS
D9 LED
D10 RFM SS
D11-D13 SPI

SDA & SCL (A4, A5) are used with flash mem.
There are also pull-ups on interrput and SDA pins.
There are no other connections as far as i know. (including pin 4 you mentioned)
cambazz



Joined: 22/03/2015 01:37:43
Messages: 5
Offline

Yes I tested with the multimeter that DIO5 is connected to pin D4.

The RFM98W module has many other DIO pins. I wonder if they are connected in any way?

So the final list is:

D2 RFM DIO0
D3 RTC interrupt
D4 RFM DIO5
D5 flash mem SS
D9 LED
D10 RFM SS
D11-D13 SPI




empeka wrote:
cambazz wrote:Hello,

The anarduino module with rfm98w is undocumented at this point. For example the DIO0 and DIO5 on the RFM98W module, are connected to pins 4 and 2
which i had to figure out by measuring.

There are many pins on the RFM98 module. How can i figure out which pins it is connected to?



D2 RFM interrupt
D3 rtc interrupt
D5 flash mem SS
D9 LED
D10 RFM SS
D11-D13 SPI

SDA & SCL (A4, A5) are used with flash mem.
There are also pull-ups on interrput and SDA pins.
There are no other connections as far as i know. (including pin 4 you mentioned)
 
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