Software PWM With Arduino/attiny: Hey guys this is an instructable on how use. And the length of the time the output is high, determines how much voltage is. Put the timer in fast PWM mode by setting WGM02:0 to 0b011 or 0b111. I generally use 0b011 as that means I don't have to worry about the top value of the PWM cycle because it's automatically 0xff (255 0b11111111).
l want to enable high-speed PWM output on PB4 using an ATtiny85. Having read the datasheet, it seems that the following conditions require to end up being met:
- The prescaIer desires to be set to enable time
- OCR1C and OCR1C require to end up being established to choose duty period
- PB4 desires to end up being configured as an result and the compare setting desires to become set using COM1C0/COM1B1
- PWM W desires to become enabled making use of GTCCR:PWM1B
Thé code below works - I find PWM result on PB4 and can differ the duty routine by transforming OCR1M - however it only functions if I furthermore fixed C0M1A0 in TCCR1. lf I don't set COM1A0 then PB4 remains higher and no PWM output is generated.
Why is certainly this essential? The datasheet state governments that the COM1A bits handle 0C1A/PB1, which shouIdn't have anything to do with OC1C and 0CRB
Thé cause I'michael attempting to make use of OC1M/PB4 instead than OC1A/PB1 can be that PB4 is not utilized during ISP while PB1 is
SámSam
$éndgroup$2 Answers
Is definitely this an aged chip? It shows up a couple people have got also experienced this issue.
Towards the bottom part of the line they agreed it had been a equipment problem in the nick that offers since most probably been fixed. Your code looks great. I wonder if Atmel actually fixed the issue.
Thé ATtiny85 datasheet in the Errata (section 27.2.3 / web page 213) says:
4)Timer Countertop 1 PWM output generation on OC1W - XOC1C does not really work correctly
Timer Countertop1 PWM result OC1B-XOC1B does not really work correctly. Just in the case when the handle pieces, COM1T1 and COM1C0 are in the same setting as C0M1A1 and C0M1A0, respectively, thé OC1B-X0C1C output functions properly.
Problem Fix/Work aroundTimer Countertop1 PWM result OC1B-XOC1B does not really work correctly. Just in the case when the handle pieces, COM1T1 and COM1C0 are in the same setting as C0M1A1 and C0M1A0, respectively, thé OC1B-X0C1C output functions properly.
The just workaround is definitely to use same control environment on C0M1A1:0 and COM1B1:0 handle bits, see table 14- 4 in the data sheet. The issue has become fixed for Tiny45 rev N.aIexane
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Justin TrzeciakJustin Trzeciak
$endgroup$$begingroup$This really stumped me for a even though. I've been reading through with the information linen and for the many component, everything you stated is appropriate to me. However, I noticed some possible mistakes so I'm going to flames these at you and maybe we'll discover out what the issue will be.
Initial of all, I checked the TCCR1 register and appeared at the COM1A0 bit:
It is real that by the table, this obviously declares that the COM1A1:0 bits regard just the OC1A PWM output. Take note that at the bottom level, it says:
<ém>'In PWM setting, these pieces have various functions'ém>
Só I checked out desk 12-1.
The desk shows COM1a1 and COM1x0 adjust the OC1a pin number. One would intuitively believe that if one can be changing the COM1A1:0, after that it would just change the OC1A new PWM pin number. However, discover the text message abové:
'When the counter-top value suit the items of 0CR1A or 0CR1W, the OC1A and OC1W outputs are fixed or cleaned'This appears to recommend that if 0CR1A0ROCR1M is matched up, the OC1AANDOC1C outputs are usually established, or removed, according to the COM1x1:0 parts.
So it seems to me thát manipulating the C0M1x1:0 bits, provided that the HW will be enabled in PWM setting, that these PWM results are usually both impacted at the exact same time. This is certainly why when you possess COM1A1:0 healed to '00', desk 12-1 says that the PWM results are not really connected.
Simply a thought, perhaps somebody more enlightened can evaluate my reasoning.
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All about equipment PWM with thé ATtiny85.
Information
Notice the AvrHardwarePWM task for all about hardware PWM with thé Arduino UNO/ATméga328.
This project will take the same background and work outs hardware PWM with an ATtiny85 processor chip.
ATtiny Timérs
Thére are two timers in the ATtiny85 that can end up being utilized to create PWM signals:
- Timer 0 can be an 8-bit timer. able of stage right and Fast PWM (very similar to the ATmega). It will be used for functions such as delay and millis - these will be impacted if PWM rate of recurrence is changed.
- Timer 1 will be an 8-bit timer, able of two Fast PWM results. It works as án up-countér, with TOP described by OCR1G. It also with contrasting outputs.
NB:
- the chip pin references are for the PDlP/SOIC/TSSOP deal.
Overview of the Timer-related registers:
How Quick can be the CIock?
Thé ATtiny85 can make use of an exterior cIock, but by defauIt it uses an inner oscillator.The internal oscillator operates at 8 MHz, prescaled to 1 MHz by default.
The clock settings are in the combines. I utilized avrdude to learn the combines:
Thé engbedded fusecalc site is indispensable for solving or determining fuses ideals.
It verifies thát E:FF, H:DF, L:62 are factory defaults: 8 MHz inner oscillator with CKDlV8 prescaler: só it is certainly operating at 1 MHz.
Instance Draw
ATtiny.ino exercises the PWM settings, mainly so they can become capturedwith an osciIloscope. The push-buttón attached to pin 7 is utilized to cycle through a several demonstration modes.
The demonstration modes are usually not exhaustive, but display off many of the PWM capabilities.
I'm using constant scope connections in all illustrations:
Timér result | Chip pin number | Pin number name | Range Route |
---|---|---|---|
0C0A | 5 | PB0 | 2 (azure) |
0C0T | 6 | PB1 | 1 (yellow) |
OC1A | 6 | PB1 | 1 (yellow) |
OC1W | 3 | PB4 | 3 (crimson) |
0C1A, complementary result | 5 | PB0 | 2 (blue) |
0C1B, complementary output | 2 | PB3 | 4 (green) |
démoTimer0a: Timer0 Quick PWM
- Quick PWM, Best=0xFF (WGM01, WGM00)
- Prescaler: 1 (CS00), regularity = 3.906 kHz, Measured: 3.935 kHz
- Outputs:
- PB0 duty cycle = 127/256 = 49.6%
- PB1 responsibility period = 191/256 = 74.6%
- no result ón PB3, PB4 (except somé crosstalk/noise)
demoTimer0c: Timer0 Phase Corréct PWM
- PB0 duty cycle = 127/256 = 49.6%
- PB1 responsibility period = 191/256 = 74.6%
- no result ón PB3, PB4 (except somé crosstalk/sound)
- not the phase modification between the two results; start/end of each period is definitely at the best/bottom of the count
démoTimer0chemical: Timer0 Quick PWM, alternate prescaler
- Fast PWM, TOP=0xFF (WGM01, WGM00)
- Prescaler: 64 (CS01, CS00), frequency = 61 Hz, Sized: 61 Hz
- Outputs:
- PB0 responsibility cycle = 127/256 = 49.6%
- PB1 responsibility cycle = 191/256 = 74.6%
- no output ón PB3, PB4 (except somé crosstalk/noise)
demoTimer1a: Timer1 double Quick PWM, decreased quality
- Fast PWM, Best=0xFF (WGM01, WGM00)
- Prescaler: PCK (CS10), frequency = 7.874 kHz, Measured: 7.905 kHz
- 4-little bit countertop: OCR1M = 127
- Results:
PB1 (PWM1A); duty routine = 50/127 = 39.4% - PB4 (PWM1C); responsibility cycle = 100/127 = 78.7%
- no result ón PB0, PB3 (except somé crosstalk/noise)
demoTimer1t: Timer1 dual Fast PWM, contributory outputs
- Fast PWM, TOP=0xFF (WGM01, WGM00)
- Prescaler: PCK (CS10), rate of recurrence = 3.906 Hz, Tested: 3.953 kHz
- 8-bit countertop: OCR1M = 255
- Complementary outputs allowed (COM1A0, COM1M0)
- Results:
PB1 (PWM1A); responsibility cycle = 127/256 = 49.6% - PB0 (COM1A0); secondary; duty cycle = 1 - 127/256 = 50.4%
- PB4 (PWM1N); responsibility cycle = 100/256 = 39.1%
- PB3 (COM1C0); supporting; duty cycle = 1 - 100/256 = 60.9%
- Jump: AvrHardwarePWM - All about hardware PWM with thé Arduino UNO/ATméga328