This repository contains the code base for the Hero microcontroller. It is responsible for direct motor control and reading from various sensors.
Hero board's documentation: https://www.ctr-electronics.com/hro.html. Under the Tech Resources tab, you can find the Hero user guide and software documentation.
You need to have the phenoix framework (available under the Tech Resources tab in the link above) and Visual Studio 2017 or newer (community edition is enough) installed.
This protocol is a simple variable-length protocol. A valid packet consists of a sequence of bytes of the following format
0xff count databytes checksum
0xff is the header byte
count is a single byte specifying the opcode of this message and the length of the data bytes. The two most significaint bits indicate the opcode. The lower 6 bits indicate the number of bytes in the databytes section. Alternatively, we can say that we have 10 header bits in total. Because the size is determined by 6 bits, the valid range for the length of the data bytes are between 0 and 63 (because we have 6 bits that we can use, and 2^6=64).
| Opcode | Value | Description |
|---|---|---|
| 00 | Stop | Stops and disables all motors |
| 01 | Direct Control | Passes percent output values to each talon in order of their IDs |
| 10 | PID Control | Given target values, the Hero will adjust the motors to meet those targets |
| 11 | Reserved | Reserved for future use |
databytes consist of arbitrary bytes whose length is specified by the lower 6 bits of count . These must be in the same order everytime. The order is as follows:
- Drive Front Left
- Drive Front Right
- Drive Back Left
- Drive Back Right
- Bucket Ladder
- Bucket Extension
- Bucket Chain Driver
- Basket Lifter
checksum is the sum of all bytes before it modulo 256.
For example,
0xff 0xc4 0x12 0x13 0x14 0x15 0x11
is a valid byte sequence for this protocol. Note that 0xc4 = 0b11000100 = 196. The most significant 2 bits are set to 1, which indicates an opcode of 3 which is reserved. The next 6 represents that we have 0b100 = 4 data bytes. They are 0x12 0x13 0x14 0x15. Finally, we find the sum of 0xff 0xc4 0x12 0x13 0x14 0x15 = 0x211, and mod by 256 = 0x100, and as the result we got 0x11 as the checksum.
This protocol is a simple variable-length protocol. A valid packet consists of a sequence of bytes of the following format
0xff count databytes checksum
0xff is the header byte
count is a single byte specifying the length of the data bytes. We require the most significant 2 bits of the count byte to set to 1. Alternatively, we can say that we have 10 header bits in total. Because the 2 upper bits are set to 1, the valid range for the length of the data bytes are between 0 and 63 (because we have 6 bits that we can use, and 2^6=64).
databytes consist of arbitrary bytes whose length is specified by count (with the upper 2 bits set to 0, of course).
checksum is the sum of all bytes before it modulo 256.
For example,
0xff 0xc4 0x12 0x13 0x14 0x15 0x11
is a valid byte sequence for this protocol. Note that 0xc4 = 0b11000100 = 196. The most significant 2 bits are set to 1, so this byte represents that we have 0b100 = 4 data bytes. They are 0x12 0x13 0x14 0x15. Finally, we find the sum of 0xff 0xc4 0x12 0x13 0x14 0x15 = 0x211, and mod by 256 = 0x100, and as the result we got 0x11 as the checksum.