Try changing the %n in the print statement to print out a 32 bit value. I think you will see that it is an address in the PRU address space.
Graham From: beagleboard@googlegroups.com [mailto:beagleboard@googlegroups.com] On Behalf Of Walter Cromer Sent: Tuesday, April 20, 2021 10:34 AM To: BeagleBoard <beagleboard@googlegroups.com> Subject: [beagleboard] Strange behavior of value returned from PRU with RPMSG I am using a Beaglebone Black and C to read analog inputs with PRU0 and return the data to a host program using RPMSG. Basically, I read the data from FIFO0 fine, strip the step id from it and copy it into an element of a character array in the PRU code. <start of snippet of PRU code> Data = HWREG(SOC_ADC_TSC_0_REGS + TSC_ADC_SS_FIFODATA(0)); if ((Data & 0x000F0000) == 0) { // checking the step id tag for step 0 // if step == 0, strip off the step and put the data in array DetBSample DetBSample[sampleno] = Data & 0xFFF; memcpy(payload, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24); // this came from TI's sample code, best I can tell it just preloads and end of string character in the whole string. ltoa((long)DetBSample[sampleno], payload); // put the value in DetBSample[sampleno] in the character string payload // now send the payload to the host pru_rpmsg_send(&transport, dst, src, payload, 24); This code compiles and runs fine. On the host side, I do this when I'm kicked by the PRU. (This is a snippet so brackets may not match!) /* Poll until we receive a message from the PRU and then print it */ result = read(pollfds[0].fd, readBuf, MAX_BUFFER_SIZE); if (result > 0) { Volts = atof(readBuf)*ADC_Res; printf("Message %d received from PRU:%s or %x\n", i, readBuf, readBuf); printf("Volts read: %.3f\n",Volts); The output is strange though (snippet below). The message #, string value of readBuf and Volts are all correct. But when I output readBug as hex, it never changes. I thought it might be the address of readBuf but it doesn't appear to be. The voltage matches the input we're providing from a bench power supply and the decimal value is correct. It's just that this hex value doesn't change. Message 97 received from PRU:3742 or 4b50b0 Volts read: 1.644 Message 98: Sent to PRU Message 98 received from PRU:3744 or 4b50b0 Volts read: 1.645 Message 99: Sent to PRU Message 99 received from PRU:3743 or 4b50b0 Volts read: 1.645 Received 100 messages, closing /dev/rpmsg_pru30 -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com <mailto:beagleboard+unsubscr...@googlegroups.com> . To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/784129ee-1cf5-4438-881e-7ac6621e7aben%40googlegroups.com <https://groups.google.com/d/msgid/beagleboard/784129ee-1cf5-4438-881e-7ac6621e7aben%40googlegroups.com?utm_medium=email&utm_source=footer> . -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/002701d7364e%24a2ff0550%24e8fd0ff0%24%40comcast.net.
