Added TinyDebugSerial to attiny85

One of the challenges of 8-pins attiny85 is that we do not have Serial Monitor debugging after flashing the hex into the IC. As per my previous blog, without debugging output, we cannot be sure what is happening when the attiny is up and running.

While browsing the arduino forum, I came across this site that wrote about several methods to have serial communications to the attiny. Since I only have CSN & CE pins free when the nRF24L01 is not transmitting, I decide to go with the TinyDebugSerial method of serial output. This method will use the attiny85 PB3 pin and transmit to the Serial-TTL receiver or an Arduino.

You can use a USB-Serial TTL module or an Arduino to receive the serial transmitted by the attiny and only use one pin on the attiny. Since I have an extra USB FTDI to Serial TTL breakout board, I will use this board and also power up the attiny and nRF24L01 using the on-board selectable 5V/3.3V regulator. Choose 3.3V jumper as the nRF24L01 can only take up to 3.8V only.

attiny/nRF24L01 with FTDI BoB

The above image is my prototype with 6-pin ICSP header on top of the attiny85 with connections to the nRF24L01 and TX to the RX of the FTDI. When I am programming the attiny85, I had to remove the nRF24L01 transceiver and Vcc jumper cable from the FTDI as my USBtinyISP is providing power to the attiny85 and prevent the nRF24L01 transceiver from interfering the attiny85 during flashing/programming the chip. Once the USBtinyISP programming is done, I can immediately "see" the output from the USB-FTDI on my console/serial monitor. 

attiny to USB-Serial TTL

The first step is to install the new tiny cores from https://code.google.com/p/arduino-tiny/ and compile the codes with the new cores to make it everything is working without the extra codes. Once everything is working fine, I added the following lines to my codes :-


#include <TinyDebugSerial.h>
TinyDebugSerial mySerial = TinyDebugSerial();

// Put this in setup()
  mySerial.begin( 9600 );

// Put this in loop()

  mySerial.print("Sent :");
  mySerial.println(buffer);


The rest of the code is at the github repo under libraries/mirf85/examples at the link below.

When I tried to compiled it, I got the following compilation errors due to using an older version of WinAVR on Windows or older avr-gcc on Mac OSX software on the Arduino IDE 1.0.1.

"R_AVR_13_PCREL against symbol `exit' defined in .fini9 section in" 

Here are the links to the fixes and I will not rewrite it here... it have to do with an updated ld file for the avr.

Windows fixes :- Arduino Forum
Max OSX fixes :-  Arduino Forum

Once the above fixes is applied, I was able to see serial output on my USB-Serial on the serial monitor or any terminal program.

Summary Links :-
- Updated github repo with TinyDebugSerial
- Serial Comms with attiny
- Atmel AVR TinyISP
- Attiny cores https://code.google.com/p/arduino-tiny/
- Window fixes for R_AVR_13_PCREL
- Mac OSX fixes for R_AVR_13_PCREL

Process of getting attiny85 to work with nRF24L01 on RF24 libraries

While getting Arduino or Raspberry Pi to talk to nRF24L01 was fun and challenging, trying to make it work for a 8-pin attiny85 is a whole different experience... without serial monitor or printf debugging to the display, after the firmware was flash into the attiny85, you could only guess what is happenning or not happening when nothing was received on the nRF24L01 receiver side...

Initially, I just assume that since the Atmel attiny85 does not have hardware SPI, getting nRF24L01 talking to the attiny was not so possible... but after a few searches and reading up some blogs and forums, things seems to look brighter...

attiny85 pinout

The second challenge was the usable pins on the attiny85, with 8 pins and two used by power and ground, only six pins are available... and the nRF24L01 radios uses the usual SPI - MOSI, MISO, CLK plus another two pins for SS/CSN and CE leaving only the reset pin unused.

The third challenge was size of the firmware, unlike Arduino UNO using atmega328 with 32Kb of flash, the attiny85 only have 8Kb of flash, so optimizing the code was really important, and this is the largest flash size of the attiny x5 series. See this link for the attiny comparison chart.

With the help of Alex from Insidegadgets.com, I start from a scaled down mirf codes ( mirf was the initial libraries for nRF24L01 written in C for the AVR ) using notepad, WinAVR and avrdude to compile and flash the firmware into the attiny85. Then I was using a ported version to Arduino IDE that makes things much more easier as Arduino IDE can still support USBtinyISP, the programmer I was using to flash firmware into the attiny85.

After a few unsuccessful retries, I decide to use a different approach and found on Arduino forum that someone had modified the Arduino SPI and mirf into ther attiny85 version called SPI85 and mirf85. After matching all the channels, data rate and CRC, I manage to get some packets on Serial Monitor with a mirf library on the Arduino UNO.

Since all my libraries are using RF24 for both the Arduino & Raspberry Pi, having a mirf library isn't too much useful for me. I went through all the codes and default settings and managed to configure the mirf to be compatible with RF24 library.

attiny85 nRF24L01 USBtinyISP

Here are a summary of differences between both the mirf and RF24 library :-

Data rate :
mirf : 2Mbps as it uses the default registry setting of the nRF24L01
RF24 : configurable via setDataRate()

CRC length :
mirf : 8bit CRC length
To make it work for the RF24, change the following header files directly :-
mirf85.h
#define mirf_CONFIG ((1<<EN_CRC) | (1<<CRCO) )

RF24 : configurable via setCRCLength()

Node addressing :
mirf : serv1 or clie1 ( 5 bytes in ascii format )
To talk to RF24 receiver, use the following format,  :-

    byte RADDR[] = {0xe2, 0xf0, 0xf0, 0xf0, 0xf0};
    byte TADDR[] = {0xe3, 0xf0, 0xf0, 0xf0, 0xf0};


RF24: f0f0f0f0e2 format ( 5 bytes in hex format )

Optional settings :-

Enable Dynamic Payload :
I had my RF24 receiver with dynamic payload enabled so that I only need to set the payload size on transmitter only and can use different payload length instead of the max length.. set the below to mirf codes to enable dynamic payload.

mirf :
Mirf.configRegister( FEATURE, 1<<EN_DPL );
Mirf.configRegister( DYNPD, 1<<DPL_P0 | 1<<DPL_P1 | 1<<DPL_P2 | 1<<DPL_P3 | 1<<DPL_P4 | 1<<DPL_P5 );

I've compiled all the SPI85 and mirf85 files at github repo at the summary links below.

Summary Links :-
- nRF24L01 for attiny85 on github
- Insidegadgets.com
- Arduino forum

Finally got all RPi & UNO combinations working for nRF24L01

I have finally setup my second Raspberry Pi with 512M memory, clone the github RF24 ( https://github.com/stanleyseow/RF24 ) and can finally test all the combinations :-

rpi-hub.cpp

sendto_hub.cpp

Possible combo :-

- Raspberry Pi as hub
- Arduino as node

- Raspberry Pi as hub
- Raspberry Pi as node

- Arduino as hub
- Arduino as node

- Aduino as hub
- Raspberry Pi as node




If anyone got the above codes tested on other platform like  Arduino Mega2560, Due or other platforms, please let me know the details and links so that I can update my summary links for others..

My latest github repo have combined forked from https://github.com/gcopeland/RF24/ and I've added some of the changes into the Raspberry Pi codes.

Do read an articl from Greg on RF24 performance enchantments at http://maniacalbits.blogspot.com/2013/04/rf24-avoiding-rx-pipe-0-for-enhanced.html



As usual, I've all summary links below :-

- Raspberry Pi as hub ( rpi-hub.cpp )
- Raspberry Pi as node ( sendto_hub.cpp )

- Arduino as hub nRF24_Arduino_as_hub
- Arduino as node nRF24_sendto_hub

Migrated RF24 codes to github

I've migrated my previous static codes to github's RF24 libs at https://github.com/stanleyseow/RF24
This is a fork from gnulnulf codes that uses dynamic rf24 RPi libraries...

This will be using the Arduino maniacbug's RF24 libraries in additional to the Raspberry Pi codes under a different folder...

Changes to take note from my initial instructions  :-

- CE is now using GPIO25
- CSN is now using GPIO8 (CE0)

Thanks to gnulnulf, you can specify the devices inside of the codes as below :-


RF24 radio("/dev/spidev0.0",8000000 , 25);

The files are located at RF24/librf24-rpi

Instructions on using github version for RPi :-

Using git, issue the following instructions :-

git clone https://github.com/gnulnulf/RF24.git

$ cd RF24

$ cd librf24-rpi/librf24

$ make                                <--- Compile the files

$ sudo make install             <--- This will install the librf24.so.1.0 into the shared libraries

$ sudo ldconfig -v | grep librf

     librf24.so.1 -> librf24.so.1.0

$ cd examples

$ make

To run the programs, type sudo ./rpi-hub or sudo ./scanner

*** You need sudo to access the spidev0.0 device

Instruction on Arduino :-

Got examples/RF24/rpi_hub_arduino

Compile and upload to the Arduino

Connect a small buzzer to digital Pin2

If everything is working, you should hear a short beep ...

Summary Links :-

https://github.com/stanleyseow/RF24 ( Arduino RF24 and RaspberryPi libs codes all in one )

Made a slot for NRF module directly onto Arduino digital pins

Once I ran out of jumper cables, I've made a slot to hold the nRF module that sits directly onto Arduino UNO digital pins.

I've change the CSN pin from pin7 to pin9 and swap the LCD pin9 to pin7. This is reflected in my latest codes below.


// Set up nRF24L01 radio on SPI pin for CE, CSN ( *** older codes uses Pin 7 instead )
RF24 radio(8,9);


LiquidCrystal lcd(10, 7, 3, 4, 5, 6);
// Make way for the SPI pins
// 10 -> LCD 4
// 7  -> LCD 6
// 3  -> LCD 11
// 4  -> LCD 12
// 5  -> LCD 13
// 6  -> LCD 14

Arduino with nRF slot directly to digital pins

I've re-wrote both the program on the Raspberry Pi and Arduino to make it more practical use. I've made the Raspberry Pi as the central hub to receive sensor data from Arduino nodes and returned back the same data to the sender for calculating the round-trip time (rtt).

You can download the updated codes at the summary links below.

I'm using all the pipes for each of the nodes, so if you want to use this codes, uncomment the pipes for different nodes to send payload to the Raspberry Pi using different node address.


// Radio pipe addresses for the 2 nodes to communicate. Uncomment for the active node
 const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };
// const uint64_t pipes[2] = { 0xF0F0F0F0E2LL, 0xF0F0F0F0D2LL };
// const uint64_t pipes[2] = { 0xF0F0F0F0E3LL, 0xF0F0F0F0D2LL };
// const uint64_t pipes[2] = { 0xF0F0F0F0F1LL, 0xF0F0F0F0D2LL };
// const uint64_t pipes[2] = { 0xF0F0F0F0F2LL, 0xF0F0F0F0D2LL };
// Pipe0 is F0F0F0F0D2 ( same as reading pipe )


*** You can either connect a small buzzer or LED to pin2 for audio/visual acknowledgement the payload once it is returned and matched the outBuffer payload sent to the RPi.


Summary Links :-

- RF24 libs/codes on github:-  https://github.com/stanleyseow/RF24 ( all Arduino & Raspberry Pi codes are on github )

Setup Nordic nRF24L01 RF modules to both Arduino UNO and Raspberry Pi

In my process of building a Wireless Sensor Network, I obtained  a few low cost RF module from Inhaos that are compatible with Nordic Semiconductor nRF24L01. My plans are to have these low cost RF modules replaces the wires for my sensor network on Arduino and connect them to Raspberry Pi as the IP gateway to the rest of the Internet.

Raspberry Pi with nRF24L01-PA-LNA with BT module and USB Wifi

This entry will show you on how to setup both Arduino UNO & Raspberry Pi to connect to these nRF24L01 modules.

Some basic information on these low cost RF modules, they communicate using SPI to the microcontroller and works on raw speed of 250Kbps, 1Mbps and 2Mbps.

I'm using the following hardware & software:-

Arduino UNO with maniacbug RF24 libraries ( http://arduino.cc/forum/index.php/topic,62222.0.html /  http://maniacbug.github.com/RF24/index.html )

Raspberry Pi Model B running Adafruit's Occidentalis V0.2 ( http://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/occidentalis-v0-dot-2 ) that support SPI.

Nordic Semiconductor Datasheet / Product Info ( http://www.nordicsemi.com/eng/Products/2.4GHz-RF/nRF24L01P )

RF modules used here :-

------------------

nRF24L01+ PA+LNA+2dBi ant

nRF24L01+ with PA & LNA and 2 dBi antenna ( http://www.elecfreaks.com/wiki/index.php?title=2.4G_Wireless_nRF24L01p_with_PA_and_LNA ), these are long range RF modules acting as hub on the Raspberry Pi.

Inhaos RF2400P

Inhaos RF2400P (with 5dBm RF power output) on BEKEN Chipset ( http://www.inhaos.com/product_info.php?products_id=35 ). They are compatible with the nRF24L01 but with higher output power of 5dBm.

nRF24L01+

nRF24L01+ ( http://www.elecfreaks.com/store/24g-wireless-nrf24l01p-p-118.html or http://store.iteadstudio.com/index.php?main_page=product_info&cPath=7&products_id=53 )

Too many to choose from, just google for the above keyword on eBay or choose the cheapest as they sells in bulk of 10 pieces for a very low cost...

*** The main differences between the regular nRF24L01+ modules and the Inhaos RF2400P modules are that the RF2400P have a higher output power of 5dBm but could not do 250Kbps speed.

I'm running my setup using 1Mbps speed.

Setting up Arduino 

Connect using jumper wires from the above pin to the nRF24L01+ modules

Upload the sketches/program to the Arduino, download it here from Dropbox. 

Arduino UNO with nRF24L01+/PA/LNA/2dBi ant

Arduino connections to the nRF24L01 modules :-

Arduino Pin 11 to RF Module Pin 6 ( MOSI)

Arduino Pin 12 to RF Module Pin 7 ( MISO )

Arduino Pin 13 to RF Module Pin 5 ( SCK )

Arduino Pin 7 to RF Module Pin 4 ( CSN )

Arduino Pin 8 to RF Module Pin 3 ( CE )

Arduino 3.3V to RF Module Pin 2 ( VCC / 3.3V ) *** RF Module can only take 3.3V 

Arduino GND to RF Module Pin 1 ( GND )

RF Module Pin 8 (IRQ) is not connected

*** All the other pins are 5V tolerant

Optional LCD Module to display the received payload & payload length :-

I'm using Arduino Pin 7 & 8 for the SPI because my LCD module is using the following pins :-

Arduino Pin 9 - LCD Pin 4

Arduino Pin 10 - LCD Pin 6

Arduino Pin 3 - LCD Pin 11

Arduino Pin 4 - LCD Pin 12

Arduino Pin 5 - LCD Pin 13

Arduino Pin 6 - LCD Pin 14

Arduino Pin 2 - connect to buzzer ( for sound feedback when it received a valid packet )

Setting up Raspberry Pi

Upgrade your Raspberry Pi firmware to Adafruit Occidentalis V0.2 that support hardware SPI.

Download the above firmware and flash your SD card according to the instruction on Adafruit/Raspberry Pi website.

Refer to the two Raspberry Pi GPIO pinout and the physical pinout.

Raspberry Pi GPIO

GPIO with pin functions

RPi GPIO9    (Pin 21)  to RF Module Pin 7 ( MISO )

RPi GPIO10  (Pin 19)  to RF Module Pin 6 ( MOSI )

RPi GPIO 11 (Pin 23)  to RF Module Pin 5 ( SCK )

RPi GPIO8    (Pin 24)  to RF Module Pin 3 ( CE )

RPi GPIO 25 (Pin 22)  to RF Module Pin 4 ( CSN )

RPI 3.3V       (Pin 17)  to RF Module Pin 2 ( VCC/3.3V )

RPi Gnd        (Pin 25)  to RF Module Pin 1 (GND)

Instructions on using github version for RPi :-

Using git, issue the following instructions on Raspberry Pi command prompt :-

$ git clone https://github.com/stanleyseow/RF24.git

$ cd RF24

$ cd librf24-rpi/librf24

$ make                                <--- Compile the files

$ sudo make install              <--- This will install the librf24.so.1.0 into the shared libraries

$ sudo ldconfig -v | grep librf

     librf24.so.1 -> librf24.so.1.0

$ cd ../examples/

$ make

To run the programs, type 

$ sudo ./rpi-hub 

or 

$ sudo ./scanner

*** You need sudo/root to access the spidev0.0 device

Instruction on Arduino :-

Got examples/RF24/rpi_hub_arduino ( make sure the pins matches the above Arduino pinout )

Compile and upload to the Arduino

Optional :- Connect a small buzzer to digital Pin2 to hear a beep when the packet is returned to sender

If everything is working, you should see a screenshot below :-

rpi-hub screenshot

Summary Links :-

- Raspberry Pi firmware :- Adafruit Occidentalis-v0.2

- RF24 library (Arduino & RPi libs) on Github https://github.com/stanleyseow/RF24

Datasheets :-

- Nordic nRF24L01+ Datasheet :- nRF24L01+ DS

Forum :-
- Raspberry Pi Forum on nRF24L01 Click here
- Arduino Forum on maniacbug nRf24L01 driver Click here