Thank you, Joakim, but I don't think it is correct. Starting from 0, bit No. 3 of the IEEE802154_FCF_VERS_V1 (Hex 0x10 or binary: 0001 0000) have the value 1, thus 0 to 3 represent 8 to 11 on buf[1]. therefor, the bit No. 3, in 0x10, is set on bit No. 11 of the FCF.
Not sure if the below illustration will be on a layout. ---buf[0] buf[1] 0000 0000 0000 0000 <-- FCF ------------- 0001 0000 <-- IEEE802154_FCF_VERS_V1 This means that the Frame version is not really set probably or this file "RIOT/sys/net/link_layer/ieee802154/ieee802154.c" follows a different FCF format!! Am I correct or did I misunderstand that? Ahed ________________________________ From: Aboodi Ahed Hussein Ali Sent: Wednesday, November 27, 2019 5:58 AM To: RIOT OS developers list <devel@riot-os.org> Subject: IEEEE 802.15.4 FCF Format in "RIOT/sys/net/link_layer/ieee802154/ieee802154.c" Hi all, I am having a hard time understanding how the "ieee802154_set_frame_hdr" function, found in this link<https://github.com/RIOT-OS/RIOT/blob/master/sys/net/link_layer/ieee802154/ieee802154.c>, sets the Frame Control Field (FCF) for 802.15.4 frame header. Following the IEEE 802.15.4 FCF format, frame version should be at the 12-13th bit of the 2-byte FCF, while in the function code, the frame version was set at the 11th bit. Does it uses different FCF format or am I missing something? This is the first part of the function: size_t ieee802154_set_frame_hdr(uint8_t *buf, const uint8_t *src, size_t src_len, const uint8_t *dst, size_t dst_len, le_uint16_t src_pan, le_uint16_t dst_pan, uint8_t flags, uint8_t seq) { int pos = 3; /* 0-1: FCS, 2: seq */ uint8_t type = (flags & IEEE802154_FCF_TYPE_MASK); buf[0] = flags; buf[1] = IEEE802154_FCF_VERS_V1; // IEEE802154_FCF_VERS_V1 is defined as 0x10 if (((src_len != 0) && (src == NULL)) || ((dst_len != 0) && (dst == NULL))) { return 0; } ... ... The first two bytes of the *buf represent the FCF. I would appreciate it if someone explains or provides the FCF format that RIOT-OS uses. Thank you, Ahed
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