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armsrc/felica: add polling response time slot support to felica_sim_lite

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Make sure we respond in a valid time slot.
We were responding too early, the first time slot (which is always allowed) starts after 512 * 64 / fc.

Also, respond in incremental time slots. We could have used a fixed time slot (#0 is always allowed), but by using incremental time slots we have a better chance the reader will get our response in the expected time frame.
(when our timing is wrong, we have a risk of responding too early when using the first slot, and too late when using the last slot. Slots in the middle of the allowed range have the best chance)
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pieterg 2021-11-19 14:59:45 +01:00 • committed by GitHub
commit 1ec2e95437
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8
armsrc/felica.c
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@ -735,6 +735,7 @@ void felica_sim_lite(uint8_t *uid) {
if (FelicaFrame.crc_ok) {
if (FelicaFrame.framebytes[2] == 6 && FelicaFrame.framebytes[3] == 0) {
static uint8_t timeslot = 0;
// polling... there are two types of polling we answer to
if (FelicaFrame.framebytes[6] == 0) {
@ -747,6 +748,13 @@ void felica_sim_lite(uint8_t *uid) {
curlen = R_POLL1_LEN;
listenmode = false;
}
if (timeslot > FelicaFrame.framebytes[7]) {
// framebytes[7] contains the maximum time slot in which we are allowed to respond (#0..#15)
timeslot = 0;
}
// first time slot (#0) starts after 512 * 64 / fc, slot length equals 256 * 64 / fc
felica_nexttransfertime = GetCountSspClk() - (DELAY_AIR2ARM_AS_READER + DELAY_ARM2AIR_AS_READER) / 16 + (512 + timeslot * 256) * 64 / 16 + 1;
timeslot++; // we should use a random time slot, but responding in incremental slots should do just fine for now
}
if (FelicaFrame.framebytes[2] > 5 && FelicaFrame.framebytes[3] == 0x06) {