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firmware: use the full 11 bit US_FIDI.FI_DI_RATIO

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US_FIDI_FI_DI_RATIO_Msk is 0x7ff,
cemu rejected >= 0x400 in emu_update_fidi() and masked with 0x3ff
in card_emu_uart_update_fidi(), but update_fidi() used by
the sniffer already used 0x7ff.

-> ratios 1024..2047 are unusable in cemu, which is the entire upper
half of ISO 7816-3 Table 7 at Di=1.

A reader trying one of those in a PPS gets the proposal echoed and
accepted, after which the card keeps transmitting at the old rate.

FI_DI_RATIO is clock periods per bit -> larger ratio is a SLOWER link.
The old check rejected slow values but accepted Fi=372/Di=64, ratio 5 !?

Unify and use the register mask (= shifed by 0 so usable as value) and
reject ratios that do not fit rather than truncating to garbage dividers.

Change-Id: I6211dd5be7c5c5d2150af2aa37a403b33e6d340d
This commit is contained in:
Eric Wild
2026-07-28 17:42:32 +02:00
committed by lynxis lazus
parent 889b8d8927
commit 88a6a782a2
3 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
firmware/libcommon/source/card_emu.c
+1 -1
View File
@@ -376,7 +376,7 @@ static void emu_update_fidi(struct card_handle *ch)
int rc;
rc = iso7816_3_compute_fd_ratio(ch->F_index, ch->D_index);
if (rc > 0 && rc < 0x400) {
if (rc > 0 && rc <= (US_FIDI_FI_DI_RATIO_Msk >> US_FIDI_FI_DI_RATIO_Pos)) {
TRACE_INFO("%u: computed F(%u)/D(%u) ratio: %d\r\n", ch->num,
ch->F_index, ch->D_index, rc);
/* make sure UART uses new F/D ratio */
firmware/libcommon/source/mode_cardemu.c
+1 -1
View File
@@ -387,7 +387,7 @@ int card_emu_uart_update_fidi(uint8_t uart_chan, unsigned int fidi)
Usart *usart = get_usart_by_chan(uart_chan);
usart->US_CR |= US_CR_RXDIS | US_CR_RSTRX;
usart->US_FIDI = fidi & 0x3ff;
usart->US_FIDI = US_FIDI_FI_DI_RATIO(fidi);
usart->US_CR |= US_CR_RXEN | US_CR_STTTO;
return 0;
}
firmware/libcommon/source/simtrace_iso7816.c
+2 -2
View File
@@ -127,14 +127,14 @@ void update_fidi(Usart_info *usart, uint8_t fidi)
uint8_t di = fidi & 0xf;
int ratio = iso7816_3_compute_fd_ratio(fi, di);
if (ratio > 0 && ratio < 0x8000) {
if (ratio > 0 && ratio <= (US_FIDI_FI_DI_RATIO_Msk >> US_FIDI_FI_DI_RATIO_Pos)) {
/* make sure USART uses new F/D ratio */
usart->base->US_CR |= US_CR_RXDIS | US_CR_RSTRX;
/* disable write protection */
if (usart->base->US_WPMR) {
usart->base->US_WPMR = US_WPMR_WPKEY(0x555341);
}
usart->base->US_FIDI = (ratio & 0x7ff);
usart->base->US_FIDI = US_FIDI_FI_DI_RATIO(ratio);
usart->base->US_CR |= US_CR_RXEN | US_CR_STTTO;
//TRACE_INFO("updated USART(%u) Fi(%u)/Di(%u) ratio(%d): %u\n\r", usart->id, fi, di, ratio, usart->base->US_FIDI);
} else {