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SlashDevin / NeoSWSerial

Efficient alternative to SoftwareSerial with attachInterrupt for RX chars, simultaneous RX & TX
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Doesn't compile on ATTiny84 #21

Open gion86 opened 6 years ago

gion86 commented 6 years ago

I have the same error as in issue #3. Now I could try to use a different timer on the tiny84, timer1 should be ok?? The problem is that, from the datasheet, I see the prescaler can only be: 1, 8, 64, 256.... but no 32. So is there anything else I have to change to make it work on the tiny84 with the prescaler at 64 for example?? Should be something similar to the work of @SRGDamia1 for AtMega32...

Thanks!

SRGDamia1 commented 6 years ago

On the 32u4, I solved the missing timer 2 by picking another timer (4) with the right prescaler. It doesn't look like the ATtinyx4 has that option. I think with a different prescaler/timer speed you'd need to adjust the TICKS_PER_BIT and BITS_PER_TICK values for that speed (similar to the discussion in #19)

gion86 commented 6 years ago

Grazie Sara! ;)

I've made the changes to compile and run on the Tiny84 (I will eventually create a pull request): TCCR1A = 0x00; // "normal" operation - Normal port operation, OC1A & OC1B disconnected TCCR1B = 0x03; // 0b00000011 - Clock Select bits 11 & 10 on - prescaling source = CK/64

The timer is timer 1, and PCI_FLAG_REGISTER is GIFR (same as Tiny85).

Now that the timer is running at 8MHz/64 = 125kHz:

static const uint8_t TICKS_PER_BIT_9600 = 13; // 9600 baud bit width in units of 8us static const uint8_t TICKS_PER_BIT_31250 = 4; // 31250 baud bit width in units of 8us static const uint16_t BITS_PER_TICK_31250_Q10 = 256; // 31250 bps * 0.000008 s * 2^10 "multiplier" static const uint16_t BITS_PER_TICK_38400_Q10 = 314; // 1s/(38400 bits) * (1 tick)/(8 us) * 2^10 "multiplier"