I can't use ATTINY85 as Transmitter with 433MHZ module (with Arduino Uno works fine). Could you help me?

Hi there,

I've burned my bootloader with 8MHZ.

All I'm trying to do is to send the string below with ATTINY85. It compiles, but no data is sent :frowning:


If I compile the exactly same source-code with Arduino Uno/Nano, it works flawlessly.

Could you please help me figure out? If you have already a code which works, but uses different library, could you please share with me?

Thank you so much!

#include <RH_ASK.h>
#include <SPI.h> // Not actually used but needed to compile

RH_ASK driver(2000, 4, 3); // 200bps, TX on D3 (pin 2)

void setup() {
  // put your setup code here, to run once:


void loop() {
  // put your main code here, to run repeatedly:

    const char *msg = "512,00.00,00.00,00,0,10001";

    driver.send((uint8_t *)msg, strlen(msg));


Which ATtiny core are you using? Are you sure "Pin 3" is on the pin your radio is connected to? Are you sure you selected the 8 MHz clock rate? What are you using for a programmer?

the doc states

RH_ASK works with ATTiny85, using Arduino 1.0.5 and tinycore from Google Code Archive - Long-term storage for Google Code Project Hosting. Tested with the examples ask_transmitter and ask_receiver on ATTiny85. Caution: The RAM memory requirements on an ATTiny85 are very tight. Even the bare bones ask_transmitter sketch barely fits in eh RAM available on the ATTiny85. Its unlikely to work on smaller ATTinys such as the ATTiny45 etc. If you have wierd behaviour, consider reducing the size of RH_ASK_MAX_PAYLOAD_LEN to the minimum you can work with. Caution: the default internal clock speed on an ATTiny85 is 1MHz. You MUST set the internal clock speed to 8MHz. You can do this with Arduino IDE, tineycore and ArduinoISP by setting the board type to "ATtiny85@8MHz', setting theProgrammer to 'Arduino as ISP' and selecting Tools->Burn Bootloader. This does not actually burn a bootloader into the tiny, it just changes the fuses so the chip runs at 8MHz. If you run the chip at 1MHz, you will get RK_ASK speeds 1/8th of the expected.

Thanks so much.

Since I need a couple more code to include in the project, maybe RH_ASK would be too big for ATTINY85.

Do you know any other RF library which works with ATTINY85? Thanks.

The connections are fine.

I'm using Attiny Core [Attiny25/45/85 (no bootloader)] I don't know how to check the version.

My attiny is working great, I can make a couple of LEDs to blink with it.

The VirtualWire library takes up far less memory than RadioHead, and works great. There are plenty of tutorials on using it with the ATtiny85.

VirtualWire should indeed do the job if you keep things simple (doc states)

Caution: ATTiny85 has only 2 timers, one (timer 0) usually used for millis() and one (timer 1) for PWM analog outputs. The VirtualWire library, when built for ATTiny85, takes over timer 0, which prevents use of millis() etc but does permit analog outputs.

code could possibly be modified to use timer1 and you might want to shorten the buffer size to save ram

RCSwitch will possibly work for sending stuff out, as mentioned in the header file receiving has to be disabled

// At least for the ATTiny X4/X5, receiving has to be disabled due to
// missing libm depencies (udivmodhi4)
#if defined( __AVR_ATtinyX5__ ) or defined ( __AVR_ATtinyX4__ )
#define RCSwitchDisableReceiving

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.