Differences

This shows you the differences between two versions of the page.

--- vedirect_protocol:faq [2020-07-20 13:09] – [2. Framehandler reference implementation] mbosma
+++ vedirect_protocol:faq [2020-07-20 21:25] – [Q8: How do I calculate the TEXT checksum?] mbosma
@@ Line 79: / Line 79: @@
 ==== Q8: How do I calculate the TEXT checksum? ====
-I need to get data from a BMV, but how do I calculate the checksum?\\
+I need to get data from a BMV, but how do I check the data integrity? The [[https://www.victronenergy.com/support-and-downloads/whitepapers|VE.Direct protocol]] mentions the modulo 256 sum; what is this?\\
+**Answer:**\\
 Consider the following output:
 <code>
@@ Line 113: / Line 115: @@
 char message[] = { ... };
 for (int i = 0; i < message.length; i++) {
-   checksum += rxBuffer[i] & 255; /* Take modulo 256 in account */
+   checksum = (checksum + message[i]) & 255; /* Take modulo 256 in account */
 }