NRF52832 unexpected PWM ratehttps://devzone.nordicsemi.com/f/nordic-q-a/39101/nrf52832-unexpected-pwm-rateHello, I am using hardware PWM on NRF52832 in order to drive a MOS. I found something unexpected with the rates. i understand the PWM rate is determined by the clock divider and the counterTop value, which can be considered as the resoution in bit.en-USTelligent Community 13Tue, 02 Oct 2018 12:38:11 GMTRE: NRF52832 unexpected PWM ratehttps://devzone.nordicsemi.com/thread/151232?ContentTypeID=1Tue, 02 Oct 2018 12:38:11 GMT137ad170-7792-4731-bb38-c0d22fbe4515:911c382a-bc82-4f0b-9747-e7058be7bf93lo<p>Thank you for the return, indeed the&nbsp;wrong values&nbsp;were due to the&nbsp;rounding in the function which printed the table and a wrong prescaler (div_2), my bad. Yes i am aware that overall accuracy&nbsp;of PWM frequency is&nbsp;determined by the HF oscillator accuracy,&nbsp;i use a&nbsp;5ppm one.</p><div style="clear:both;"></div>RE: NRF52832 unexpected PWM ratehttps://devzone.nordicsemi.com/thread/151215?ContentTypeID=1Tue, 02 Oct 2018 11:56:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:88d6eb03-84cd-4fca-8480-8119f77ce781MartinBL<p><span>Hi,</span></p> <p><span>I&#39;m not sure what you are doing wrong, but the values in your table look wrong. Your formula looks alright, but when I run the numbers I get:</span></p> <table width="1056"> <tbody> <tr> <td width="124"></td> <td width="83"></td> <td colspan="12" width="849"><strong>Bit width and Counter Top</strong></td> </tr> <tr> <td></td> <td></td> <td><strong>15</strong></td> <td><strong>14</strong></td> <td><strong>13</strong></td> <td><strong>12</strong></td> <td><strong>11</strong></td> <td><strong>10</strong></td> <td><strong>9</strong></td> <td><strong>8</strong></td> <td><strong>7</strong></td> <td><strong>6</strong></td> <td><strong>5</strong></td> <td><strong>4</strong></td> </tr> <tr> <td><strong>Divider (Prescaler)</strong></td> <td><strong>F_PWM_CLK</strong></td> <td><strong>32767</strong></td> <td><strong>16383</strong></td> <td><strong>8191</strong></td> <td><strong>4095</strong></td> <td><strong>2047</strong></td> <td><strong>1023</strong></td> <td><strong>511</strong></td> <td><strong>255</strong></td> <td><strong>127</strong></td> <td><strong>63</strong></td> <td><strong>31</strong></td> <td><strong>15</strong></td> </tr> <tr> <td><strong>128</strong></td> <td><strong>125000</strong></td> <td>3.815</td> <td>7.630</td> <td>15.261</td> <td>30.525</td> <td>61.065</td> <td>122.190</td> <td>244.618</td> <td>490.196</td> <td>984.252</td> <td>1984.127</td> <td>4032.258</td> <td>8333.333</td> </tr> <tr> <td><strong>64</strong></td> <td><strong>250000</strong></td> <td>7.630</td> <td>15.260</td> <td>30.521</td> <td>61.050</td> <td>122.130</td> <td>244.379</td> <td>489.237</td> <td>980.392</td> <td>1968.504</td> <td>3968.254</td> <td>8064.516</td> <td>16666.667</td> </tr> <tr> <td><strong>32</strong></td> <td><strong>500000</strong></td> <td>15.259</td> <td>30.519</td> <td>61.043</td> <td>122.100</td> <td>244.260</td> <td>488.759</td> <td>978.474</td> <td>1960.784</td> <td>3937.008</td> <td>7936.508</td> <td>16129.032</td> <td>33333.333</td> </tr> <tr> <td><strong>16</strong></td> <td><strong>1000000</strong></td> <td>30.519</td> <td>61.039</td> <td>122.085</td> <td>244.200</td> <td>488.520</td> <td>977.517</td> <td>1956.947</td> <td>3921.569</td> <td>7874.016</td> <td>15873.016</td> <td>32258.065</td> <td>66666.667</td> </tr> <tr> <td><strong>8</strong></td> <td><strong>2000000</strong></td> <td>61.037</td> <td>122.078</td> <td>244.170</td> <td>488.400</td> <td>977.040</td> <td>1955.034</td> <td>3913.894</td> <td>7843.137</td> <td>15748.031</td> <td>31746.032</td> <td>64516.129</td> <td>133333.333</td> </tr> <tr> <td><strong>4</strong></td> <td><strong>4000000</strong></td> <td>122.074</td> <td>244.156</td> <td>488.341</td> <td>976.801</td> <td>1954.079</td> <td>3910.068</td> <td>7827.789</td> <td>15686.275</td> <td>31496.063</td> <td>63492.063</td> <td>129032.258</td> <td>266666.667</td> </tr> <tr> <td><strong>1</strong></td> <td><strong>16000000</strong></td> <td>488.296</td> <td>976.622</td> <td>1953.363</td> <td>3907.204</td> <td>7816.317</td> <td>15640.274</td> <td>31311.155</td> <td>62745.098</td> <td>125984.252</td> <td>253968.254</td> <td>516129.032</td> <td>1066666.667</td> </tr> </tbody> </table> <p>These values seem pretty spot on when I test with a logic analyzer.&nbsp;</p> <p>PS: Remember that the tolerance of your PWM frequency will only&nbsp;ever be as accurate as your high frequency clock source. So if you rely on the internal HF RC Oscillator (HFINT) your accuracy <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/clock.html?cp=2_1_0_18_3_0#unique_1861058799">can be off by as much as 6 %</a>.</p><div style="clear:both;"></div>