topic Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM in i.MX RT Crossover MCUs

RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

purongyu — Fri, 02 Nov 2018 08:41:35 GMT

Hello

我使用 PWM1模块3的PwmA通道在 STS[RF](Reload Flag) 置位时触发 eDMA0通道8 写 VALX寄存器。通过DMA0传输，使PWM1模块3的PwmA通道输出8个占空比不同、周期相同的波形，用来表示一个字节的数据，如下图表示0x04，发送的8个周期分别代表位 0000 0100。

随后使用 PWM2模块3的PwmA通道捕获上面输出的波形来触发 DMA0通道4 读捕获寄存器。DMA0通道4 用来传输 CVAL2寄存器的值到定义的数组； DMA0通道4 链接通道5 来传输CVAL2CYC的值；通道5 链接通道6 来传输CVAL3的值；通道6 链接通道7 来传输CVAL3CYC的值。PWM2模块3的PwmA通道设置为 A0 下降沿捕获， A1 上升沿捕获， A0捕获 && A1捕获触发DMA传输。

调试时，发现了几个问题：

1. PWM1 产生波形时，有可能会丢掉第一个周期，如图：这理论上是发送 0x02（0000 0010），实际发送的却少了一个周期（000 0010）

2. 在PWM1发送的波形无误的情况下，PWM2捕获波形后通过DMA传输到内存的数据可能会漏掉第一个周期。如下: 图是PWM1发送的波形0x0a（00001010），是正确的；g_CVALx和g_CVALxCYC是PWM2捕获下图中波形，通过DMA传输到内存的捕获寄存器数据。出错的寄存机值见 g_CVAL2[7]；g_CVAL2[7] 理论值是要比g_CVAL2[6] （26288）大，实际g_CVAL2[7]的值是初始化值7（数组初始化时赋的初始值）。

g_CVAL2[0] = 24181
g_CVAL2CYC[0] = 4
g_CVAL3[0] = 24392
g_CVAL3CYC[0] = 4

g_CVAL2[1] = 24482
g_CVAL2CYC[1] = 4
g_CVAL3[1] = 24692
g_CVAL3CYC[1] = 4

g_CVAL2[2] = 24783
g_CVAL2CYC[2] = 4
g_CVAL3[2] = 24994
g_CVAL3CYC[2] = 4

g_CVAL2[3] = 25084
g_CVAL2CYC[3] = 4
g_CVAL3[3] = 25294
g_CVAL3CYC[3] = 4

g_CVAL2[4] = 25385
g_CVAL2CYC[4] = 4
g_CVAL3[4] = 25294 //在这里，本来DMA传输过来的应该是比 g_CVAL2[4] 大的值，结果传输的是上一次捕获的
g_CVAL3CYC[4] = 4     //g_CVAL3[3] 的值

g_CVAL2[5] = 25987
g_CVAL2CYC[5] = 4
g_CVAL3[5] = 25896
g_CVAL3CYC[5] = 4

g_CVAL2[6] = 26288
g_CVAL2CYC[6] = 4
g_CVAL3[6] = 26499
g_CVAL3CYC[6] = 4

g_CVAL2[7] = 7
g_CVAL2CYC[7] = 70 //7 和 70 是初始值，本来应该是和前面一样有正确数据的，
g_CVAL3[7] = 7                //这部分，DMA没传输数据过来
g_CVAL3CYC[7] = 70

3. 在PWM1发送的波形无误的情况下，DMA传输到内存的数据可能是上次捕获的捕获寄存器值。如上: 见 g_CVAL3[4] 和 g_CVAL3[3]；g_CVAL3[4] 理论值是要比 g_CVAL3[3] （25294）大，实际g_CVAL3[4]的值等于g_CVAL3[3] 的值。

4. 在计数器从65535->0时，如果在等于0时捕获成功，则可能出现这种情况，CVAL2 捕获值为0，但CVAL2CYC捕获的值没加1.如下：g_CVAL2CYC[3] = 1，理论上应该 g_CVAL2CYC[3] = 2

g_CVAL2[1] = 64934
g_CVAL2CYC[1] = 1
g_CVAL3[1] = 65144
g_CVAL3CYC[1] = 1

g_CVAL2[2] = 65235
g_CVAL2CYC[2] = 1
g_CVAL3[2] = 65446
g_CVAL3CYC[2] = 1

g_CVAL2[3] = 0
g_CVAL2CYC[3] = 1 //这里理论值应该是2，实际捕获到的是1
g_CVAL3[3] = 210
g_CVAL3CYC[3] = 2

g_CVAL2[4] = 300
g_CVAL2CYC[4] = 2
g_CVAL3[4] = 391
g_CVAL3CYC[4] = 2

5. 以上第1、2、3、点，在输出波形的频率越低时出现的概率越小，在10K时，基本上不会出现这些错误，在500k时，这些错误出现的概率就比较多了。

我估计应该是PWM的配置问题，是我哪里没有配置好吗？需要注意哪些方面？

我将我测试的代码放进附录。

Best regards,

Torstei

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

jimmychan — Thu, 22 Nov 2018 07:03:01 GMT

which SDK are you using?

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

purongyu — Fri, 23 Nov 2018 02:18:25 GMT

Hello

The version in "fsl_edma.h" is "Version 2.1.2", as shown below:

The version in "fsl_pwm.h" is "Version 2.0.0", as shown below:

After verification, the library versions of these two modules are up to date.

Best regards,

Aldo.

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

shunanli-b46639 — Fri, 30 Nov 2018 02:58:39 GMT

Hello purongyu

could you please provide your contact information? I want to know some background about this project. Thanks!

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

shunanli-b46639 — Thu, 06 Dec 2018 07:38:59 GMT

purongyu‌，could you provide the "bsp_bdm.h" file? I cannot find it in your attachment.

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

purongyu — Thu, 06 Dec 2018 07:55:36 GMT

Hello

My phone number: +86 13058085495

Background of the project: This is a programmer project, this is a chip programming protocol.
The only statement in the file "bsp_bdm.h" is the test function (void BDM( void );).
Thank you for your help!

Best regards,

Aldo.

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

shunanli-b46639 — Mon, 10 Dec 2018 06:50:25 GMT

Hi Purong,

Per our talk, you had implemented the your target fucntion by Qtimer and eDMA. Could you provide the codes of Qtimer and eDMA? Then I can compare them with that of FLEXPWM and eDMA to try to figure out the problem. Thanks!

Re: RT1052CVL5B uses FLEXPWM and eDMA output and capture PWM

purongyu — Sat, 29 Dec 2018 07:31:20 GMT

Hello

抱歉，最近实在有点忙，刚刚整理了tmr实现的代码，把测试代码发上来。

有以下3个文件：

Best regards,

Aldo.