diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e623132
--- /dev/null
+++ b/README.md
@@ -0,0 +1,5 @@
+## Samana network components
+
+This repository contains transmitters and receivers implemented using [nRF24L01+](https://www.nordicsemi.com/eng/Products/2.4GHz-RF/nRF24L01P) wireless chip.
+
+Implementation for Raspberry PI can be found in the [rpi](rpi/) directory, and (tiny)[tiny/] directory contains implementation for ATtiny85 MCU.
diff --git a/bcm2835 b/bcm2835
deleted file mode 120000
index 628ee19..0000000
--- a/bcm2835
+++ /dev/null
@@ -1 +0,0 @@
-../bcm2835-1.38
\ No newline at end of file
diff --git a/common.c b/common.c
index 1fae3bf..9da9e40 100644
--- a/common.c
+++ b/common.c
@@ -33,28 +33,6 @@ void common_config()
     spi_transfern(buf, 2);
 }
 
-void ptx()
-{
-    // read CONFIG register
-    uint8_t buf[2] = { 0, 0 };
-    spi_transfern(buf, 2);
-
-    buf[0] = 0b00100000; // write to CONFIG
-    buf[1] |= 0 << 0; // PRX
-    spi_transfern(buf, 2);
-}
-
-void prx()
-{
-    // read CONFIG register
-    uint8_t buf[2] = { 0, 0 };
-    spi_transfern(buf, 2);
-
-    buf[0] = 0b00100000; // write to CONFIG
-    buf[1] |= 1 << 0; // PRX
-    spi_transfern(buf, 2);
-}
-
 void prx_addr()
 {
     // RX_ADDR_P0
diff --git a/common.h b/common.h
index aef80d6..1e115ad 100644
--- a/common.h
+++ b/common.h
@@ -3,21 +3,59 @@
 
 #include <stdint.h>
 
+/**
+ * Configure NRF24 registers that are common for prx and ptr.
+ */
 void common_config();
-void ptx();
-void prx();
+
+/**
+ * Set prx listen address.
+ */
 void prx_addr();
+
+/**
+ * Set receiver address and listen address for acks.
+ */
 void receiver_addr();
 
+/**
+ * Go to POWER UP state.
+ */
 void power_up();
+
+/**
+ * Got to POWER DOWN state.
+ */
 void power_down();
 
+/**
+ * Check if data is ready in the RX FIFO by querying which data pipe has data available.
+ */
 uint8_t rx_data_ready();
-uint8_t get_rx_data();
 
+/**
+ * Clock in received data from RX FIFO.
+ */
+uint8_t get_rx_data(uint8_t *rx_data);
+
+/**
+ * Flush TX FIFO. In prx this holds ACK payloads.
+ */
 void flush_tx();
+
+/**
+ * Flush RX FIFO.
+ */
 void flush_rx();
+
+/**
+ * Clear interrupt flags.
+ */
 void clean_int_flags();
+
+/**
+ * Flush TX and RX FIFOs and clear interrupt flags.
+ */
 void clean_up();
 
 #endif
diff --git a/platform.h b/platform.h
index 32cf52f..66d95c2 100644
--- a/platform.h
+++ b/platform.h
@@ -3,6 +3,10 @@
 
 #include <stdint.h>
 
+/**
+ * Contains function definitions which implementations are platform specific.
+ */
+
 void print(char *str);
 void println(char *str);
 void print_buf(uint8_t *buf, uint8_t n);
diff --git a/receiver.c b/receiver.c
index 32611e9..4c21342 100644
--- a/receiver.c
+++ b/receiver.c
@@ -1,6 +1,17 @@
 #include "platform.h"
 #include "common.h"
 
+void prx()
+{
+    // read CONFIG register
+    uint8_t buf[2] = { 0, 0 };
+    spi_transfern(buf, 2);
+
+    buf[0] = 0b00100000; // write to CONFIG
+    buf[1] |= 1 << 0; // PRX
+    spi_transfern(buf, 2);
+}
+
 void clean_rx_dr_int()
 {
     uint8_t status = spi_transfer(0xFF);
diff --git a/receiver.h b/receiver.h
index fb0e1aa..2ef8ac7 100644
--- a/receiver.h
+++ b/receiver.h
@@ -1,7 +1,19 @@
 #ifndef RECEIVER_H
 #define RECEIVER_H
 
+/**
+ * Configure prx specific registers.
+ */
+void prx();
+
+/**
+ * Clean RX Data Ready interrupt flag.
+ */
 void clean_rx_dr_int();
+
+/**
+ * A loop where receiver puts ACK payloads and handles received messages.
+ */
 void receiver_loop() __attribute__ ((noreturn));
 
 #endif
diff --git a/rpi/README.md b/rpi/README.md
new file mode 100644
index 0000000..e07b2c5
--- /dev/null
+++ b/rpi/README.md
@@ -0,0 +1,5 @@
+## Building
+
+Make sure `bcm2835` symlink is pointing to a directory which contains [bcm2835](http://www.airspayce.com/mikem/bcm2835/) library. By default symlink points to a sibling directory of this repository. Version of the library is specified in the contents of the symlink.
+
+Build both transmitter and receiver binaries by running `build.sh`.
diff --git a/rpi/bcm2835 b/rpi/bcm2835
new file mode 120000
index 0000000..7ba204d
--- /dev/null
+++ b/rpi/bcm2835
@@ -0,0 +1 @@
+../../bcm2835-1.38
\ No newline at end of file
diff --git a/rpi/build.sh b/rpi/build.sh
index f8e90e3..3913a5a 100755
--- a/rpi/build.sh
+++ b/rpi/build.sh
@@ -1,14 +1,14 @@
 #!/usr/bin/env bash
 
-gcc -g -o ptx -std=gnu99 -Wall -I ../bcm2835/src/ \
-  ../bcm2835/src/bcm2835.c \
+gcc -g -o ptx -std=gnu99 -Wall -I bcm2835/src/ \
+  bcm2835/src/bcm2835.c \
   ../common.c \
   ../transmitter.c \
   platform.c \
   ptx.c
 
-gcc -g -o prx -std=gnu99 -Wall -I ../bcm2835/src/ \
-  ../bcm2835/src/bcm2835.c \
+gcc -g -o prx -std=gnu99 -Wall -I bcm2835/src/ \
+  bcm2835/src/bcm2835.c \
   ../common.c \
   ../receiver.c \
   platform.c \
diff --git a/tiny/Makefile b/tiny/Makefile
index 5bc2da2..3257359 100644
--- a/tiny/Makefile
+++ b/tiny/Makefile
@@ -42,7 +42,7 @@ endif
 cflags+=-include definitions.h
 
 # https://github.com/thegaragelab/tinytemplate library
-tinytpl=../tinytemplate
+tinytpl=tinytemplate
 cflags+=-I $(tinytpl)/firmware/include
 srcs+= \
 	$(tinytpl)/firmware/shared/uart_send.c \
diff --git a/tiny/README.md b/tiny/README.md
new file mode 100644
index 0000000..a19f103
--- /dev/null
+++ b/tiny/README.md
@@ -0,0 +1,25 @@
+## Building
+
+Make sure `tinytemplate` symlink is pointing to a directory which contains checked out [tinytemplate](https://github.com/thegaragelab/tinytemplate) repository. By default symlink points to a sibling directory of this repository. Commit id of the repository is specified in the contents of symplink.
+
+Makefile accepts the following arguments:
+
+|Argument|Possible Values|Notes                                                              |
+|--------|---------------|-------------------------------------------------------------------|
+|name    |ptx&#124;prx            |Binary (primary transmitter or primary receiver) to build |
+|avrType |attiny85&#124;attiny2313|Controller type. Tested only with attiny85                |
+|dudeHost|alarmpi&#124;...        |When specified runs `avrdude` on the specified host       |
+
+Most common make commands are `elf` (compile) and `flash` (compile and write to MCU). Flashing is done using a Raspberry Pi which has MCU connected via SPI.
+
+For example, the following command would compile primary transmitter and flash it to ATtiny85 connected to Raspberry PI running as alarmpi2:
+
+``` bash
+make name=ptx avrType=attiny85 dudeHost=alarmpi2 flash
+```
+
+## Hardware
+
+Code assumes [three wire](http://nerdralph.blogspot.com/2014/01/nrf24l01-control-with-3-attiny85-pins.html) setup where CSN clock is held by a capacitor and is controlled by SCK pin before and after transfers.
+
+Logging is enabled via UART on `PB4`.
diff --git a/tiny/definitions.h b/tiny/definitions.h
index 066131a..fce6b39 100644
--- a/tiny/definitions.h
+++ b/tiny/definitions.h
@@ -3,6 +3,10 @@
 
 #include <avr/io.h>
 
+/**
+ * This overrides definitions in hardware.h of the tinytemplate library.
+ */
+
 #define UART_ENABLED
 #define BAUD_RATE 57600
 
diff --git a/tiny/platform.c b/tiny/platform.c
index 9e04e34..37e8490 100644
--- a/tiny/platform.c
+++ b/tiny/platform.c
@@ -54,4 +54,5 @@ void spi_transfern(uint8_t *buf, uint8_t n)
 
 void ce_high()
 {
+    // CE is conntected to VCC.
 }
diff --git a/tiny/tiny_spi.c b/tiny/tiny_spi.c
index 046200b..cd0769e 100644
--- a/tiny/tiny_spi.c
+++ b/tiny/tiny_spi.c
@@ -3,6 +3,11 @@
 
 #include "tiny_spi.h"
 
+/**
+ * Thank you goes to https://github.com/JChristensen/tinySPI/blob/master/tinySPI.cpp
+ * for implementing SPI in C.
+ */
+
 void tiny_spi_begin(void)
 {
     USICR &= ~(_BV(USISIE) | _BV(USIOIE) | _BV(USIWM1));
@@ -12,9 +17,6 @@ void tiny_spi_begin(void)
     SPI_DDR_PORT &= ~_BV(DI_DD_PIN);    //set the DI pin as input
 
     USICR &= ~_BV(USICS0); // SPI MODE 0
-
-    //SPI_DDR_PORT |= _BV(SPI_CSN_PIN);
-    //SPI_PORT |= _BV(SPI_CSN_PIN);
 }
 
 uint8_t tiny_spi_crank(uint8_t spiData)
@@ -29,16 +31,14 @@ uint8_t tiny_spi_crank(uint8_t spiData)
 
 void before_transfer()
 {
-    //SPI_PORT &= ~_BV(SPI_CSN_PIN);
     SPI_PORT &= ~_BV(USCK_DD_PIN);  // SCK low will pull CSN low as well
     _delay_us(16);  // allow CSN to settle
 }
 
 void after_transfer()
 {
-    //SPI_PORT |= _BV(SPI_CSN_PIN);
     SPI_PORT |= _BV(USCK_DD_PIN);  // SCK high will pull CSN high as well
-    _delay_us(128);  // allow csn to settle
+    _delay_us(128);  // allow CSN to settle
 }
 
 void tiny_spi_transfern(uint8_t *buf, uint8_t n)
diff --git a/tiny/tiny_spi.h b/tiny/tiny_spi.h
index d9b0105..8a28c6e 100644
--- a/tiny/tiny_spi.h
+++ b/tiny/tiny_spi.h
@@ -6,10 +6,8 @@
 #define SPI_PORT PORTB
 #define SPI_DDR_PORT DDRB
 #define USCK_DD_PIN DDB2
-#define DO_DD_PIN DDB1
-#define DI_DD_PIN DDB0
-
-#define SPI_CSN_PIN DDB3
+#define DO_DD_PIN DDB1 // DO is MISO on ATtiny85
+#define DI_DD_PIN DDB0 // DI is MOSI on ATtiny85
 
 void tiny_spi_begin();
 uint8_t tiny_spi_transfer(uint8_t spiData);
diff --git a/tiny/tinytemplate b/tiny/tinytemplate
new file mode 120000
index 0000000..2822b51
--- /dev/null
+++ b/tiny/tinytemplate
@@ -0,0 +1 @@
+../../tinytemplate-2db013c
\ No newline at end of file
diff --git a/tinytemplate b/tinytemplate
deleted file mode 120000
index 02aa5c0..0000000
--- a/tinytemplate
+++ /dev/null
@@ -1 +0,0 @@
-../tinytemplate
\ No newline at end of file
diff --git a/transmitter.c b/transmitter.c
index 494283f..053a31c 100644
--- a/transmitter.c
+++ b/transmitter.c
@@ -1,6 +1,17 @@
 #include "platform.h"
 #include "common.h"
 
+void ptx()
+{
+    // read CONFIG register
+    uint8_t buf[2] = { 0, 0 };
+    spi_transfern(buf, 2);
+
+    buf[0] = 0b00100000; // write to CONFIG
+    buf[1] |= 0 << 0; // PRX
+    spi_transfern(buf, 2);
+}
+
 void tx_payload()
 {
     // W_TX_PAYLOAD command
diff --git a/transmitter.h b/transmitter.h
index e615951..9707a89 100644
--- a/transmitter.h
+++ b/transmitter.h
@@ -3,11 +3,34 @@
 
 #include <stdint.h>
 
+/**
+ * Configure ptx specific registers.
+ */
+void ptx();
+
+/**
+ * Transmit payload.
+ */
 void tx_payload();
+
+/**
+ * Check if max retransmits has been reached.
+ */
 uint8_t max_retransmits_reached();
-uint8_t tx_data_sent();
+
+/**
+ * Clear max retransmits reached flag.
+ */
 void clean_max_rt_int();
 
+/**
+ * Check if data has been sent, which means that ACK has been received with or without payload.
+ */
+uint8_t tx_data_sent();
+
+/**
+ * Configure and send predefined payload,
+ */
 void send_payload();
 
 #endif