
Online UART bitrate calculator for AVR-microcontrollers. Without entering anything, you can get a list of the UBRR settings for many popular clock speeds, and serial port bit rates. What makes this program special, is the fact that you can tell it what serial port bit rate you want, and it will tell you all the possible clock speeds that will generate your desired serial port bit rate. You can also give it a clock speed, and it will tell you all the possible serial port bit rates that can be producted with that clock speed. This is very handy when you are searching through your "junk pile", looking for the right crystal, or oscillator to generate a given serial port bit rate.
Please note, that the colors will change, depending on your data bits+parity selection. Please see the Atmel manual for your AVR for more details about how the data bits+parity, and U2X=1 settings affect the maximum allowable error rate.
UBRR and clock speed are 0.1% or less off
UBRR and clock speed are 0.5% or less off
UBRR and clock speed are 1.0% or less off
UBRR and clock speed are 2.0% or less off
UBRR and clock speed are 3.0% or less off
UBRR and clock speed are outside of the absolute maximum error rate
fCPU = 1 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 207 | 0x00CF | 300.48 | 0.2% | 416 | 0x01A0 | 299.76 | -0.1% |
600 | 103 | 0x0067 | 600.96 | 0.2% | 207 | 0x00CF | 600.96 | 0.2% |
900 | 68 | 0x0044 | 905.8 | 0.6% | 138 | 0x008A | 899.28 | -0.1% |
1200 | 51 | 0x0033 | 1201.92 | 0.2% | 103 | 0x0067 | 1201.92 | 0.2% |
1800 | 34 | 0x0022 | 1785.71 | -0.8% | 68 | 0x0044 | 1811.59 | 0.6% |
2400 | 25 | 0x0019 | 2403.85 | 0.2% | 51 | 0x0033 | 2403.85 | 0.2% |
3600 | 16 | 0x0010 | 3676.47 | 2.1% | 34 | 0x0022 | 3571.43 | -0.8% |
4800 | 12 | 0x000C | 4807.69 | 0.2% | 25 | 0x0019 | 4807.69 | 0.2% |
9600 | 6 | 0x0006 | 8928.57 | -7% | 12 | 0x000C | 9615.38 | 0.2% |
14.4 K | 3 | 0x0003 | 15.625 K | 8.5% | 8 | 0x0008 | 13.889 K | -3.5% |
19.2 K | 2 | 0x0002 | 20.833 K | 8.5% | 6 | 0x0006 | 17.857 K | -7% |
28.8 K | 1 | 0x0001 | 31.25 K | 8.5% | 3 | 0x0003 | 31.25 K | 8.5% |
33.6 K | 1 | 0x0001 | 31.25 K | -7% | 3 | 0x0003 | 31.25 K | -7% |
38.4 K | 1 | 0x0001 | 31.25 K | -18.6% | 2 | 0x0002 | 41.667 K | 8.5% |
56 K | 0 | 0x0000 | 62.5 K | 11.6% | 1 | 0x0001 | 62.5 K | 11.6% |
57.6 K | 0 | 0x0000 | 62.5 K | 8.5% | 1 | 0x0001 | 62.5 K | 8.5% |
76.8 K | 0 | 0x0000 | 62.5 K | -18.6% | 1 | 0x0001 | 62.5 K | -18.6% |
115.2 K | 0 | 0x0000 | 62.5 K | -45.7% | 0 | 0x0000 | 125 K | 8.5% |
128 K | 0 | 0x0000 | 62.5 K | -51.2% | 0 | 0x0000 | 125 K | -2.3% |
153.6 K | 0 | 0x0000 | 62.5 K | -59.3% | 0 | 0x0000 | 125 K | -18.6% |
230.4 K | 0 | 0x0000 | 62.5 K | -72.9% | 0 | 0x0000 | 125 K | -45.7% |
fCPU = 1.8432 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 383 | 0x017F | 300 | 0% | 767 | 0x02FF | 300 | 0% |
600 | 191 | 0x00BF | 600 | 0% | 383 | 0x017F | 600 | 0% |
900 | 127 | 0x007F | 900 | 0% | 255 | 0x00FF | 900 | 0% |
1200 | 95 | 0x005F | 1200 | 0% | 191 | 0x00BF | 1200 | 0% |
1800 | 63 | 0x003F | 1800 | 0% | 127 | 0x007F | 1800 | 0% |
2400 | 47 | 0x002F | 2400 | 0% | 95 | 0x005F | 2400 | 0% |
3600 | 31 | 0x001F | 3600 | 0% | 63 | 0x003F | 3600 | 0% |
4800 | 23 | 0x0017 | 4800 | 0% | 47 | 0x002F | 4800 | 0% |
9600 | 11 | 0x000B | 9600 | 0% | 23 | 0x0017 | 9600 | 0% |
14.4 K | 7 | 0x0007 | 14.4 K | 0% | 15 | 0x000F | 14.4 K | 0% |
19.2 K | 5 | 0x0005 | 19.2 K | 0% | 11 | 0x000B | 19.2 K | 0% |
28.8 K | 3 | 0x0003 | 28.8 K | 0% | 7 | 0x0007 | 28.8 K | 0% |
33.6 K | 2 | 0x0002 | 38.4 K | 14.3% | 6 | 0x0006 | 32.914 K | -2% |
38.4 K | 2 | 0x0002 | 38.4 K | 0% | 5 | 0x0005 | 38.4 K | 0% |
56 K | 1 | 0x0001 | 57.6 K | 2.9% | 3 | 0x0003 | 57.6 K | 2.9% |
57.6 K | 1 | 0x0001 | 57.6 K | 0% | 3 | 0x0003 | 57.6 K | 0% |
76.8 K | 1 | 0x0001 | 57.6 K | -25% | 2 | 0x0002 | 76.8 K | 0% |
115.2 K | 0 | 0x0000 | 115.2 K | 0% | 1 | 0x0001 | 115.2 K | 0% |
128 K | 0 | 0x0000 | 115.2 K | -10% | 1 | 0x0001 | 115.2 K | -10% |
153.6 K | 0 | 0x0000 | 115.2 K | -25% | 1 | 0x0001 | 115.2 K | -25% |
230.4 K | 0 | 0x0000 | 115.2 K | -50% | 0 | 0x0000 | 230.4 K | 0% |
fCPU = 2 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 416 | 0x01A0 | 299.76 | -0.1% | 832 | 0x0340 | 300.12 | 0% |
600 | 207 | 0x00CF | 600.96 | 0.2% | 416 | 0x01A0 | 599.52 | -0.1% |
900 | 138 | 0x008A | 899.28 | -0.1% | 277 | 0x0115 | 899.28 | -0.1% |
1200 | 103 | 0x0067 | 1201.92 | 0.2% | 207 | 0x00CF | 1201.92 | 0.2% |
1800 | 68 | 0x0044 | 1811.59 | 0.6% | 138 | 0x008A | 1798.56 | -0.1% |
2400 | 51 | 0x0033 | 2403.85 | 0.2% | 103 | 0x0067 | 2403.85 | 0.2% |
3600 | 34 | 0x0022 | 3571.43 | -0.8% | 68 | 0x0044 | 3623.19 | 0.6% |
4800 | 25 | 0x0019 | 4807.69 | 0.2% | 51 | 0x0033 | 4807.69 | 0.2% |
9600 | 12 | 0x000C | 9615.38 | 0.2% | 25 | 0x0019 | 9615.38 | 0.2% |
14.4 K | 8 | 0x0008 | 13.889 K | -3.5% | 16 | 0x0010 | 14.706 K | 2.1% |
19.2 K | 6 | 0x0006 | 17.857 K | -7% | 12 | 0x000C | 19.231 K | 0.2% |
28.8 K | 3 | 0x0003 | 31.25 K | 8.5% | 8 | 0x0008 | 27.778 K | -3.5% |
33.6 K | 3 | 0x0003 | 31.25 K | -7% | 6 | 0x0006 | 35.714 K | 6.3% |
38.4 K | 2 | 0x0002 | 41.667 K | 8.5% | 6 | 0x0006 | 35.714 K | -7% |
56 K | 1 | 0x0001 | 62.5 K | 11.6% | 3 | 0x0003 | 62.5 K | 11.6% |
57.6 K | 1 | 0x0001 | 62.5 K | 8.5% | 3 | 0x0003 | 62.5 K | 8.5% |
76.8 K | 1 | 0x0001 | 62.5 K | -18.6% | 2 | 0x0002 | 83.333 K | 8.5% |
115.2 K | 0 | 0x0000 | 125 K | 8.5% | 1 | 0x0001 | 125 K | 8.5% |
128 K | 0 | 0x0000 | 125 K | -2.3% | 1 | 0x0001 | 125 K | -2.3% |
153.6 K | 0 | 0x0000 | 125 K | -18.6% | 1 | 0x0001 | 125 K | -18.6% |
230.4 K | 0 | 0x0000 | 125 K | -45.7% | 0 | 0x0000 | 250 K | 8.5% |
fCPU = 3.6864 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 767 | 0x02FF | 300 | 0% | 1535 | 0x05FF | 300 | 0% |
600 | 383 | 0x017F | 600 | 0% | 767 | 0x02FF | 600 | 0% |
900 | 255 | 0x00FF | 900 | 0% | 511 | 0x01FF | 900 | 0% |
1200 | 191 | 0x00BF | 1200 | 0% | 383 | 0x017F | 1200 | 0% |
1800 | 127 | 0x007F | 1800 | 0% | 255 | 0x00FF | 1800 | 0% |
2400 | 95 | 0x005F | 2400 | 0% | 191 | 0x00BF | 2400 | 0% |
3600 | 63 | 0x003F | 3600 | 0% | 127 | 0x007F | 3600 | 0% |
4800 | 47 | 0x002F | 4800 | 0% | 95 | 0x005F | 4800 | 0% |
9600 | 23 | 0x0017 | 9600 | 0% | 47 | 0x002F | 9600 | 0% |
14.4 K | 15 | 0x000F | 14.4 K | 0% | 31 | 0x001F | 14.4 K | 0% |
19.2 K | 11 | 0x000B | 19.2 K | 0% | 23 | 0x0017 | 19.2 K | 0% |
28.8 K | 7 | 0x0007 | 28.8 K | 0% | 15 | 0x000F | 28.8 K | 0% |
33.6 K | 6 | 0x0006 | 32.914 K | -2% | 13 | 0x000D | 32.914 K | -2% |
38.4 K | 5 | 0x0005 | 38.4 K | 0% | 11 | 0x000B | 38.4 K | 0% |
56 K | 3 | 0x0003 | 57.6 K | 2.9% | 7 | 0x0007 | 57.6 K | 2.9% |
57.6 K | 3 | 0x0003 | 57.6 K | 0% | 7 | 0x0007 | 57.6 K | 0% |
76.8 K | 2 | 0x0002 | 76.8 K | 0% | 5 | 0x0005 | 76.8 K | 0% |
115.2 K | 1 | 0x0001 | 115.2 K | 0% | 3 | 0x0003 | 115.2 K | 0% |
128 K | 1 | 0x0001 | 115.2 K | -10% | 3 | 0x0003 | 115.2 K | -10% |
153.6 K | 1 | 0x0001 | 115.2 K | -25% | 2 | 0x0002 | 153.6 K | 0% |
230.4 K | 0 | 0x0000 | 230.4 K | 0% | 1 | 0x0001 | 230.4 K | 0% |
fCPU = 4 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 832 | 0x0340 | 300.12 | 0% | 1666 | 0x0682 | 299.94 | 0% |
600 | 416 | 0x01A0 | 599.52 | -0.1% | 832 | 0x0340 | 600.24 | 0% |
900 | 277 | 0x0115 | 899.28 | -0.1% | 555 | 0x022B | 899.28 | -0.1% |
1200 | 207 | 0x00CF | 1201.92 | 0.2% | 416 | 0x01A0 | 1199.04 | -0.1% |
1800 | 138 | 0x008A | 1798.56 | -0.1% | 277 | 0x0115 | 1798.56 | -0.1% |
2400 | 103 | 0x0067 | 2403.85 | 0.2% | 207 | 0x00CF | 2403.85 | 0.2% |
3600 | 68 | 0x0044 | 3623.19 | 0.6% | 138 | 0x008A | 3597.12 | -0.1% |
4800 | 51 | 0x0033 | 4807.69 | 0.2% | 103 | 0x0067 | 4807.69 | 0.2% |
9600 | 25 | 0x0019 | 9615.38 | 0.2% | 51 | 0x0033 | 9615.38 | 0.2% |
14.4 K | 16 | 0x0010 | 14.706 K | 2.1% | 34 | 0x0022 | 14.286 K | -0.8% |
19.2 K | 12 | 0x000C | 19.231 K | 0.2% | 25 | 0x0019 | 19.231 K | 0.2% |
28.8 K | 8 | 0x0008 | 27.778 K | -3.5% | 16 | 0x0010 | 29.412 K | 2.1% |
33.6 K | 6 | 0x0006 | 35.714 K | 6.3% | 14 | 0x000E | 33.333 K | -0.8% |
38.4 K | 6 | 0x0006 | 35.714 K | -7% | 12 | 0x000C | 38.462 K | 0.2% |
56 K | 3 | 0x0003 | 62.5 K | 11.6% | 8 | 0x0008 | 55.556 K | -0.8% |
57.6 K | 3 | 0x0003 | 62.5 K | 8.5% | 8 | 0x0008 | 55.556 K | -3.5% |
76.8 K | 2 | 0x0002 | 83.333 K | 8.5% | 6 | 0x0006 | 71.429 K | -7% |
115.2 K | 1 | 0x0001 | 125 K | 8.5% | 3 | 0x0003 | 125 K | 8.5% |
128 K | 1 | 0x0001 | 125 K | -2.3% | 3 | 0x0003 | 125 K | -2.3% |
153.6 K | 1 | 0x0001 | 125 K | -18.6% | 2 | 0x0002 | 166.667 K | 8.5% |
230.4 K | 0 | 0x0000 | 250 K | 8.5% | 1 | 0x0001 | 250 K | 8.5% |
fCPU = 7.3728 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 1535 | 0x05FF | 300 | 0% | 3071 | 0x0BFF | 300 | 0% |
600 | 767 | 0x02FF | 600 | 0% | 1535 | 0x05FF | 600 | 0% |
900 | 511 | 0x01FF | 900 | 0% | 1023 | 0x03FF | 900 | 0% |
1200 | 383 | 0x017F | 1200 | 0% | 767 | 0x02FF | 1200 | 0% |
1800 | 255 | 0x00FF | 1800 | 0% | 511 | 0x01FF | 1800 | 0% |
2400 | 191 | 0x00BF | 2400 | 0% | 383 | 0x017F | 2400 | 0% |
3600 | 127 | 0x007F | 3600 | 0% | 255 | 0x00FF | 3600 | 0% |
4800 | 95 | 0x005F | 4800 | 0% | 191 | 0x00BF | 4800 | 0% |
9600 | 47 | 0x002F | 9600 | 0% | 95 | 0x005F | 9600 | 0% |
14.4 K | 31 | 0x001F | 14.4 K | 0% | 63 | 0x003F | 14.4 K | 0% |
19.2 K | 23 | 0x0017 | 19.2 K | 0% | 47 | 0x002F | 19.2 K | 0% |
28.8 K | 15 | 0x000F | 28.8 K | 0% | 31 | 0x001F | 28.8 K | 0% |
33.6 K | 13 | 0x000D | 32.914 K | -2% | 26 | 0x001A | 34.133 K | 1.6% |
38.4 K | 11 | 0x000B | 38.4 K | 0% | 23 | 0x0017 | 38.4 K | 0% |
56 K | 7 | 0x0007 | 57.6 K | 2.9% | 15 | 0x000F | 57.6 K | 2.9% |
57.6 K | 7 | 0x0007 | 57.6 K | 0% | 15 | 0x000F | 57.6 K | 0% |
76.8 K | 5 | 0x0005 | 76.8 K | 0% | 11 | 0x000B | 76.8 K | 0% |
115.2 K | 3 | 0x0003 | 115.2 K | 0% | 7 | 0x0007 | 115.2 K | 0% |
128 K | 3 | 0x0003 | 115.2 K | -10% | 6 | 0x0006 | 131.657 K | 2.9% |
153.6 K | 2 | 0x0002 | 153.6 K | 0% | 5 | 0x0005 | 153.6 K | 0% |
230.4 K | 1 | 0x0001 | 230.4 K | 0% | 3 | 0x0003 | 230.4 K | 0% |
fCPU = 8 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 1666 | 0x0682 | 299.94 | 0% | 3332 | 0x0D04 | 300.03 | 0% |
600 | 832 | 0x0340 | 600.24 | 0% | 1666 | 0x0682 | 599.88 | 0% |
900 | 555 | 0x022B | 899.28 | -0.1% | 1110 | 0x0456 | 900.09 | 0% |
1200 | 416 | 0x01A0 | 1199.04 | -0.1% | 832 | 0x0340 | 1200.48 | 0% |
1800 | 277 | 0x0115 | 1798.56 | -0.1% | 555 | 0x022B | 1798.56 | -0.1% |
2400 | 207 | 0x00CF | 2403.85 | 0.2% | 416 | 0x01A0 | 2398.08 | -0.1% |
3600 | 138 | 0x008A | 3597.12 | -0.1% | 277 | 0x0115 | 3597.12 | -0.1% |
4800 | 103 | 0x0067 | 4807.69 | 0.2% | 207 | 0x00CF | 4807.69 | 0.2% |
9600 | 51 | 0x0033 | 9615.38 | 0.2% | 103 | 0x0067 | 9615.38 | 0.2% |
14.4 K | 34 | 0x0022 | 14.286 K | -0.8% | 68 | 0x0044 | 14.493 K | 0.6% |
19.2 K | 25 | 0x0019 | 19.231 K | 0.2% | 51 | 0x0033 | 19.231 K | 0.2% |
28.8 K | 16 | 0x0010 | 29.412 K | 2.1% | 34 | 0x0022 | 28.571 K | -0.8% |
33.6 K | 14 | 0x000E | 33.333 K | -0.8% | 29 | 0x001D | 33.333 K | -0.8% |
38.4 K | 12 | 0x000C | 38.462 K | 0.2% | 25 | 0x0019 | 38.462 K | 0.2% |
56 K | 8 | 0x0008 | 55.556 K | -0.8% | 17 | 0x0011 | 55.556 K | -0.8% |
57.6 K | 8 | 0x0008 | 55.556 K | -3.5% | 16 | 0x0010 | 58.824 K | 2.1% |
76.8 K | 6 | 0x0006 | 71.429 K | -7% | 12 | 0x000C | 76.923 K | 0.2% |
115.2 K | 3 | 0x0003 | 125 K | 8.5% | 8 | 0x0008 | 111.111 K | -3.5% |
128 K | 3 | 0x0003 | 125 K | -2.3% | 7 | 0x0007 | 125 K | -2.3% |
153.6 K | 2 | 0x0002 | 166.667 K | 8.5% | 6 | 0x0006 | 142.857 K | -7% |
230.4 K | 1 | 0x0001 | 250 K | 8.5% | 3 | 0x0003 | 250 K | 8.5% |
fCPU = 10 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 2082 | 0x0822 | 300.05 | 0% | 4166 | 0x1046 | 299.98 | 0% |
600 | 1041 | 0x0411 | 599.81 | 0% | 2082 | 0x0822 | 600.1 | 0% |
900 | 693 | 0x02B5 | 900.58 | 0.1% | 1388 | 0x056C | 899.93 | 0% |
1200 | 520 | 0x0208 | 1199.62 | 0% | 1041 | 0x0411 | 1199.62 | 0% |
1800 | 346 | 0x015A | 1801.15 | 0.1% | 693 | 0x02B5 | 1801.15 | 0.1% |
2400 | 259 | 0x0103 | 2403.85 | 0.2% | 520 | 0x0208 | 2399.23 | 0% |
3600 | 173 | 0x00AD | 3591.95 | -0.2% | 346 | 0x015A | 3602.31 | 0.1% |
4800 | 129 | 0x0081 | 4807.69 | 0.2% | 259 | 0x0103 | 4807.69 | 0.2% |
9600 | 64 | 0x0040 | 9615.38 | 0.2% | 129 | 0x0081 | 9615.38 | 0.2% |
14.4 K | 42 | 0x002A | 14.535 K | 0.9% | 86 | 0x0056 | 14.368 K | -0.2% |
19.2 K | 32 | 0x0020 | 18.939 K | -1.4% | 64 | 0x0040 | 19.231 K | 0.2% |
28.8 K | 21 | 0x0015 | 28.409 K | -1.4% | 42 | 0x002A | 29.07 K | 0.9% |
33.6 K | 18 | 0x0012 | 32.895 K | -2.1% | 36 | 0x0024 | 33.784 K | 0.5% |
38.4 K | 15 | 0x000F | 39.063 K | 1.7% | 32 | 0x0020 | 37.879 K | -1.4% |
56 K | 10 | 0x000A | 56.818 K | 1.5% | 21 | 0x0015 | 56.818 K | 1.5% |
57.6 K | 10 | 0x000A | 56.818 K | -1.4% | 21 | 0x0015 | 56.818 K | -1.4% |
76.8 K | 7 | 0x0007 | 78.125 K | 1.7% | 15 | 0x000F | 78.125 K | 1.7% |
115.2 K | 4 | 0x0004 | 125 K | 8.5% | 10 | 0x000A | 113.636 K | -1.4% |
128 K | 4 | 0x0004 | 125 K | -2.3% | 9 | 0x0009 | 125 K | -2.3% |
153.6 K | 3 | 0x0003 | 156.25 K | 1.7% | 7 | 0x0007 | 156.25 K | 1.7% |
230.4 K | 2 | 0x0002 | 208.333 K | -9.6% | 4 | 0x0004 | 250 K | 8.5% |
fCPU = 11.0592 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 2303 | 0x08FF | 300 | 0% | 4607 | 0x11FF | 300 | 0% |
600 | 1151 | 0x047F | 600 | 0% | 2303 | 0x08FF | 600 | 0% |
900 | 767 | 0x02FF | 900 | 0% | 1535 | 0x05FF | 900 | 0% |
1200 | 575 | 0x023F | 1200 | 0% | 1151 | 0x047F | 1200 | 0% |
1800 | 383 | 0x017F | 1800 | 0% | 767 | 0x02FF | 1800 | 0% |
2400 | 287 | 0x011F | 2400 | 0% | 575 | 0x023F | 2400 | 0% |
3600 | 191 | 0x00BF | 3600 | 0% | 383 | 0x017F | 3600 | 0% |
4800 | 143 | 0x008F | 4800 | 0% | 287 | 0x011F | 4800 | 0% |
9600 | 71 | 0x0047 | 9600 | 0% | 143 | 0x008F | 9600 | 0% |
14.4 K | 47 | 0x002F | 14.4 K | 0% | 95 | 0x005F | 14.4 K | 0% |
19.2 K | 35 | 0x0023 | 19.2 K | 0% | 71 | 0x0047 | 19.2 K | 0% |
28.8 K | 23 | 0x0017 | 28.8 K | 0% | 47 | 0x002F | 28.8 K | 0% |
33.6 K | 20 | 0x0014 | 32.914 K | -2% | 40 | 0x0028 | 33.717 K | 0.3% |
38.4 K | 17 | 0x0011 | 38.4 K | 0% | 35 | 0x0023 | 38.4 K | 0% |
56 K | 11 | 0x000B | 57.6 K | 2.9% | 24 | 0x0018 | 55.296 K | -1.3% |
57.6 K | 11 | 0x000B | 57.6 K | 0% | 23 | 0x0017 | 57.6 K | 0% |
76.8 K | 8 | 0x0008 | 76.8 K | 0% | 17 | 0x0011 | 76.8 K | 0% |
115.2 K | 5 | 0x0005 | 115.2 K | 0% | 11 | 0x000B | 115.2 K | 0% |
128 K | 4 | 0x0004 | 138.24 K | 8% | 10 | 0x000A | 125.673 K | -1.8% |
153.6 K | 4 | 0x0004 | 138.24 K | -10% | 8 | 0x0008 | 153.6 K | 0% |
230.4 K | 2 | 0x0002 | 230.4 K | 0% | 5 | 0x0005 | 230.4 K | 0% |
fCPU = 14.7456 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 3071 | 0x0BFF | 300 | 0% | 6143 | 0x17FF | 300 | 0% |
600 | 1535 | 0x05FF | 600 | 0% | 3071 | 0x0BFF | 600 | 0% |
900 | 1023 | 0x03FF | 900 | 0% | 2047 | 0x07FF | 900 | 0% |
1200 | 767 | 0x02FF | 1200 | 0% | 1535 | 0x05FF | 1200 | 0% |
1800 | 511 | 0x01FF | 1800 | 0% | 1023 | 0x03FF | 1800 | 0% |
2400 | 383 | 0x017F | 2400 | 0% | 767 | 0x02FF | 2400 | 0% |
3600 | 255 | 0x00FF | 3600 | 0% | 511 | 0x01FF | 3600 | 0% |
4800 | 191 | 0x00BF | 4800 | 0% | 383 | 0x017F | 4800 | 0% |
9600 | 95 | 0x005F | 9600 | 0% | 191 | 0x00BF | 9600 | 0% |
14.4 K | 63 | 0x003F | 14.4 K | 0% | 127 | 0x007F | 14.4 K | 0% |
19.2 K | 47 | 0x002F | 19.2 K | 0% | 95 | 0x005F | 19.2 K | 0% |
28.8 K | 31 | 0x001F | 28.8 K | 0% | 63 | 0x003F | 28.8 K | 0% |
33.6 K | 26 | 0x001A | 34.133 K | 1.6% | 54 | 0x0036 | 33.513 K | -0.3% |
38.4 K | 23 | 0x0017 | 38.4 K | 0% | 47 | 0x002F | 38.4 K | 0% |
56 K | 15 | 0x000F | 57.6 K | 2.9% | 32 | 0x0020 | 55.855 K | -0.3% |
57.6 K | 15 | 0x000F | 57.6 K | 0% | 31 | 0x001F | 57.6 K | 0% |
76.8 K | 11 | 0x000B | 76.8 K | 0% | 23 | 0x0017 | 76.8 K | 0% |
115.2 K | 7 | 0x0007 | 115.2 K | 0% | 15 | 0x000F | 115.2 K | 0% |
128 K | 6 | 0x0006 | 131.657 K | 2.9% | 13 | 0x000D | 131.657 K | 2.9% |
153.6 K | 5 | 0x0005 | 153.6 K | 0% | 11 | 0x000B | 153.6 K | 0% |
230.4 K | 3 | 0x0003 | 230.4 K | 0% | 7 | 0x0007 | 230.4 K | 0% |
fCPU = 16 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 3332 | 0x0D04 | 300.03 | 0% | 6666 | 0x1A0A | 299.99 | 0% |
600 | 1666 | 0x0682 | 599.88 | 0% | 3332 | 0x0D04 | 600.06 | 0% |
900 | 1110 | 0x0456 | 900.09 | 0% | 2221 | 0x08AD | 900.09 | 0% |
1200 | 832 | 0x0340 | 1200.48 | 0% | 1666 | 0x0682 | 1199.76 | 0% |
1800 | 555 | 0x022B | 1798.56 | -0.1% | 1110 | 0x0456 | 1800.18 | 0% |
2400 | 416 | 0x01A0 | 2398.08 | -0.1% | 832 | 0x0340 | 2400.96 | 0% |
3600 | 277 | 0x0115 | 3597.12 | -0.1% | 555 | 0x022B | 3597.12 | -0.1% |
4800 | 207 | 0x00CF | 4807.69 | 0.2% | 416 | 0x01A0 | 4796.16 | -0.1% |
9600 | 103 | 0x0067 | 9615.38 | 0.2% | 207 | 0x00CF | 9615.38 | 0.2% |
14.4 K | 68 | 0x0044 | 14.493 K | 0.6% | 138 | 0x008A | 14.388 K | -0.1% |
19.2 K | 51 | 0x0033 | 19.231 K | 0.2% | 103 | 0x0067 | 19.231 K | 0.2% |
28.8 K | 34 | 0x0022 | 28.571 K | -0.8% | 68 | 0x0044 | 28.986 K | 0.6% |
33.6 K | 29 | 0x001D | 33.333 K | -0.8% | 59 | 0x003B | 33.333 K | -0.8% |
38.4 K | 25 | 0x0019 | 38.462 K | 0.2% | 51 | 0x0033 | 38.462 K | 0.2% |
56 K | 17 | 0x0011 | 55.556 K | -0.8% | 35 | 0x0023 | 55.556 K | -0.8% |
57.6 K | 16 | 0x0010 | 58.824 K | 2.1% | 34 | 0x0022 | 57.143 K | -0.8% |
76.8 K | 12 | 0x000C | 76.923 K | 0.2% | 25 | 0x0019 | 76.923 K | 0.2% |
115.2 K | 8 | 0x0008 | 111.111 K | -3.5% | 16 | 0x0010 | 117.647 K | 2.1% |
128 K | 7 | 0x0007 | 125 K | -2.3% | 15 | 0x000F | 125 K | -2.3% |
153.6 K | 6 | 0x0006 | 142.857 K | -7% | 12 | 0x000C | 153.846 K | 0.2% |
230.4 K | 3 | 0x0003 | 250 K | 8.5% | 8 | 0x0008 | 222.222 K | -3.5% |
fCPU = 18.432 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 3839 | 0x0EFF | 300 | 0% | 7679 | 0x1DFF | 300 | 0% |
600 | 1919 | 0x077F | 600 | 0% | 3839 | 0x0EFF | 600 | 0% |
900 | 1279 | 0x04FF | 900 | 0% | 2559 | 0x09FF | 900 | 0% |
1200 | 959 | 0x03BF | 1200 | 0% | 1919 | 0x077F | 1200 | 0% |
1800 | 639 | 0x027F | 1800 | 0% | 1279 | 0x04FF | 1800 | 0% |
2400 | 479 | 0x01DF | 2400 | 0% | 959 | 0x03BF | 2400 | 0% |
3600 | 319 | 0x013F | 3600 | 0% | 639 | 0x027F | 3600 | 0% |
4800 | 239 | 0x00EF | 4800 | 0% | 479 | 0x01DF | 4800 | 0% |
9600 | 119 | 0x0077 | 9600 | 0% | 239 | 0x00EF | 9600 | 0% |
14.4 K | 79 | 0x004F | 14.4 K | 0% | 159 | 0x009F | 14.4 K | 0% |
19.2 K | 59 | 0x003B | 19.2 K | 0% | 119 | 0x0077 | 19.2 K | 0% |
28.8 K | 39 | 0x0027 | 28.8 K | 0% | 79 | 0x004F | 28.8 K | 0% |
33.6 K | 33 | 0x0021 | 33.882 K | 0.8% | 68 | 0x0044 | 33.391 K | -0.6% |
38.4 K | 29 | 0x001D | 38.4 K | 0% | 59 | 0x003B | 38.4 K | 0% |
56 K | 20 | 0x0014 | 54.857 K | -2% | 40 | 0x0028 | 56.195 K | 0.3% |
57.6 K | 19 | 0x0013 | 57.6 K | 0% | 39 | 0x0027 | 57.6 K | 0% |
76.8 K | 14 | 0x000E | 76.8 K | 0% | 29 | 0x001D | 76.8 K | 0% |
115.2 K | 9 | 0x0009 | 115.2 K | 0% | 19 | 0x0013 | 115.2 K | 0% |
128 K | 8 | 0x0008 | 128 K | 0% | 17 | 0x0011 | 128 K | 0% |
153.6 K | 7 | 0x0007 | 144 K | -6.3% | 14 | 0x000E | 153.6 K | 0% |
230.4 K | 4 | 0x0004 | 230.4 K | 0% | 9 | 0x0009 | 230.4 K | 0% |
fCPU = 20 MHz | ||||||||
---|---|---|---|---|---|---|---|---|
Bit Rate | U2Xn = 0 | U2Xn = 1 | ||||||
UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | UBRR (dec) | UBRR (hex) | Actual Bit Rate | Error | |
300 | 4166 | 0x1046 | 299.98 | 0% | 8332 | 0x208C | 300.01 | 0% |
600 | 2082 | 0x0822 | 600.1 | 0% | 4166 | 0x1046 | 599.95 | 0% |
900 | 1388 | 0x056C | 899.93 | 0% | 2777 | 0x0AD9 | 899.93 | 0% |
1200 | 1041 | 0x0411 | 1199.62 | 0% | 2082 | 0x0822 | 1200.19 | 0% |
1800 | 693 | 0x02B5 | 1801.15 | 0.1% | 1388 | 0x056C | 1799.86 | 0% |
2400 | 520 | 0x0208 | 2399.23 | 0% | 1041 | 0x0411 | 2399.23 | 0% |
3600 | 346 | 0x015A | 3602.31 | 0.1% | 693 | 0x02B5 | 3602.31 | 0.1% |
4800 | 259 | 0x0103 | 4807.69 | 0.2% | 520 | 0x0208 | 4798.46 | 0% |
9600 | 129 | 0x0081 | 9615.38 | 0.2% | 259 | 0x0103 | 9615.38 | 0.2% |
14.4 K | 86 | 0x0056 | 14.368 K | -0.2% | 173 | 0x00AD | 14.368 K | -0.2% |
19.2 K | 64 | 0x0040 | 19.231 K | 0.2% | 129 | 0x0081 | 19.231 K | 0.2% |
28.8 K | 42 | 0x002A | 29.07 K | 0.9% | 86 | 0x0056 | 28.736 K | -0.2% |
33.6 K | 36 | 0x0024 | 33.784 K | 0.5% | 73 | 0x0049 | 33.784 K | 0.5% |
38.4 K | 32 | 0x0020 | 37.879 K | -1.4% | 64 | 0x0040 | 38.462 K | 0.2% |
56 K | 21 | 0x0015 | 56.818 K | 1.5% | 44 | 0x002C | 55.556 K | -0.8% |
57.6 K | 21 | 0x0015 | 56.818 K | -1.4% | 42 | 0x002A | 58.14 K | 0.9% |
76.8 K | 15 | 0x000F | 78.125 K | 1.7% | 32 | 0x0020 | 75.758 K | -1.4% |
115.2 K | 10 | 0x000A | 113.636 K | -1.4% | 21 | 0x0015 | 113.636 K | -1.4% |
128 K | 9 | 0x0009 | 125 K | -2.3% | 19 | 0x0013 | 125 K | -2.3% |
153.6 K | 7 | 0x0007 | 156.25 K | 1.7% | 15 | 0x000F | 156.25 K | 1.7% |
230.4 K | 4 | 0x0004 | 250 K | 8.5% | 10 | 0x000A | 227.273 K | -1.4% |
If you enter a serial port bit rate, not already listed, then the serial port bit rate will be listed as the last entry on each clock speed table. If you enter a clock speed that is not already listed, then a new clock speed table will be generated as the first table, with your clock speed.
NOTE about the UBRR register(s): Some AVRs only have a single UBRR register, while other AVRs have two UBRR registers. If your AVR has only 1 UBRR register, then you can check the box "Consider only 8-bit UBRR values as being valid" to have it show you when the UBRR value is out of range for your AVR. If your AVR handles a 12-bit UBRR value, then the UBRR value in hexadecimal will be helpful to you, because it will make it easier to find the UBRRH and UBRRL values (I'm sure you can figure out what goes where).
NOTE about XMEGA AVRs: The UBRR values generated, can be used as the BSEL value in the XMEGA AVRs, if and only if you set BSCALE to zero. If there is enough interest for this calculator to support the XMEGA series, then I will add BSCALE calculations to the list, but for now, there is no easy way to to calculate BSCALE without already knowing knowing what BSEL value you want to use, so it's computationally expensive to calculate.